Mount Everest pioneer Sir Edmund Hillary may never have conquered the world's tallest peak without his climbing partner Tenzing Norgay, the Nepalese Sherpa.

Right now, across continents and time zones, dozens of figurative sherpas are at work around the world preparing for the diplomatic expedition that will culminate with Pittsburgh's G-20 meeting next month.

"The primary role of the sherpa is, just as in the Himalayas, preparing the way to the summit," said Michael Froman, President Barack Obama's deputy national security adviser for international economic affairs.

As he was for the meetings of the G-20 in London and the G-8 in Italy, Mr. Froman is the U.S. sherpa for the Pittsburgh summit, preparing, with his counterparts around the world and his colleagues in the State and Treasury departments, to confront and sometimes finesse the issues facing the globe's largest economies.

In public perception, the summit will begin with the grand formal dinners for world leaders and finance ministers at the Phipps Conservatory and Botanical Gardens in Oakland. But in a real sense, the summit has been under way for months, as diplomats and financial mandarins prepare the agenda and draft declarations that their heads of state and government will discuss in Pittsburgh.

Those contacts have continued without interruption since the April G-20 meeting in London. The consultations include a constant round of international travel, meetings and conference calls.

The international sherpas huddled for one meeting this summer in Washington. Most also met at the G-8 summit in Italy in July, and they will meet again in Washington in mid-September, as the Pittsburgh session nears.

"Because we work so closely together, we've developed a good relationship as a group," said Mr. Froman, "and there's a certain informality and ease of interaction which allows us to tackle issues of the summit, but [also] other issues between our countries as they arise."

The G-20 finance ministers, including U.S. Treasury Secretary Tim Geithner, will gather this week in London for one more session laying the groundwork for Pittsburgh. The leaders of the European Union are reported to be planning for a gathering to coordinate their pre-summit positions in Brussels on Sept. 17, the week before the summit.

Daniel M. Price, a partner with the Sidley Austin international law firm, who was Mr. Froman's predecessor as the U.S. sherpa in his former role as assistant to the president for International Economic Affairs in the Bush administration, said, "There will typically be drafting sessions among sherpas to review the declaration. The night before the summit can be a time of quite intense activity as the final positions of the leaders are hammered out."

Tony Fratto, who was chief spokesman for the Treasury Department before serving as deputy press secretary in the Bush administration, noted that the extent of these behind-the-scenes preparations allowed both for successful summits, and sometimes, for "good theater" for participants eager to impress home audiences.

Knowing the progress of behind-the-scenes negotiations, he said, some leaders will try to score domestic political points in pre-summit posturing as, "They call on the G-20 to do what they already know is going to happen."

The very depth of preparation before the leaders assemble raises the question of whether such meetings amount to grand photo ops, showcasing well-rehearsed ratifications of decisions made in advance elsewhere. Mr. Froman dismissed that characterization.

"The purpose of these summits you can look at in a couple of different ways," he said. "One is as an opportunity for leaders to get to know one another, to develop relationships, so that when they need to pick up the phone in the midst of a crisis and ask for something, there's a pre-existing sort of basis for doing so.

"Another way is an action-forcing event that mobilizes every country and international organization to come up with solutions to various problems and put those solutions out there, and then there is actually a forum where the leaders get together and work through and resolve a particular issue in the context of sitting across the table from one another."

Offering a similar point, his predecessor, Mr. Price, said, "The leaders are not gathering for a drafting session ... The key benefit of these summits is the interactions among the leaders. When you have a group that represents more than 80 percent of world [gross domestic product], the discussions and decisions carry enormous weight."

"At this point in time, except for some narrow policy differences, they're fairly precooked," Mr. Fratto said of the leaders' agenda. "By this time, they're probably negotiating the language of the communiqué."

But the current and former U.S. sherpas agreed that the leaders could and do confront and settle issues unresolved despite the meticulous preparations. Mr. Froman pointed to a widely reported encounter during the London summit where Mr. Obama was credited with brokering a last-minute accord on language involving crackdowns on tax havens -- an issue that had promoted a heated dispute between the French and Chinese delegations.

"A very interesting issue, countries with different points of view on it, and it really got worked out literally in the corner of the room between President Obama, President Hu Jintao, and President [Nicolas] Sarkozy," he said.

Trade and climate change would be among the chief issues on next month's agenda, Mr. Froman said. In addressing them, the leaders hope to increase the chances of progress for other international forums, specifically talks on climate change scheduled for later this year in Copenhagen. Their discussion on trade comes in the face of the major hurdle of reviving the long-stalled Doha Round of negotiations, named after the city where they began, to liberalize international trade.

"Given what many key allies regard as the nuanced ambivalence of the Obama administration on trade liberalization, the G-20 nations will be eager to hear the President's views on how to provide impetus to completing the Doha Round," Mr. Price said.

But on the trade issue, observers may count it a victory if the talks can simply ward off more backsliding on protectionism despite the free-trade pledges that were central to both the Washington and London meetings.

Despite pledges issued in Washington and London, Mr. Price pointed out, 17 of the G-20 countries have enacted protectionist measures of one form or another since the onset of the economic crisis. Mr. Froman argued, however, that the Washington and London pledges had produced significant if imperfect results.

"I think it has effectively constrained what otherwise might have taken place in the absence of such a pledge," he said. "While a number of countries have adopted action that might be called protectionist in one form or another, it has not had a meaningful effect [in restricting] global trade, and that was really the purpose of the protectionism pledge, to avoid the downward spiral of trade that occurred in the 1930s and ... I think it's achieved that."

Mr. Froman said that reviewing the initiatives of past meetings was an important part of this one.

"So we'll take stock of what we announced earlier, [see] where we are in the process of implementation, and what further steps need to be taken," he said. In addition, he said the leaders will continue to try to seek consensus on a vision for "the foundation for the global economic growth model ... coming out of this crisis."

Among the things the G-20 leaders will be called on to assess over time is the future of the G-20 itself. The organization began in 1997 as a forum for finance ministers. It was only in November, in the face of the cratering of the world economy, that those nations' leaders assembled for their first time under its organization.

"President Bush decided that given the severity of the crisis and its potential impact on developing countries, it was important to have a broadly representative group of leaders," Mr. Price said.

"We were in the midst of an unprecedented situation with events breaking on an almost daily basis in many countries. We thought very carefully about how to do this and, after extensive consultations with foreign leaders, concluded that the G-20 was the right format."

So while the Pittsburgh summit is only the third gathering under the G-20 banner, there is no firm decision yet on whether the format will be institutionalized. Will it outlast the financial crisis that produced it or will it revert to a forum for finance officials?

Mr. Froman said no decision has been made.

"I think it has proven to be a useful forum for dealing, certainly with the financial crisis and, I think, broader economic issues," he said. "And I think the leaders are likely to ... assess whether it has an ongoing role, but I think people have been pretty pleased with what it's done so far."