MOSCOW --When Russia seized Crimea in March, it acquired not just the Crimean landmass but also a maritime area more than three times its size with the rights to underwater resources potentially worth trillions of dollars.
Russia portrayed the takeover as reclamation of its rightful territory, drawing no attention to the oil and gas rush that had recently been heating up in the Black Sea. But the move also extended Russia's maritime boundaries, quietly giving Moscow dominion over vast oil and gas reserves while dealing a crippling blow to Ukraine's hopes for energy independence.
Moscow did so under an international accord that gives nations sovereignty over areas up to 230 miles from their shorelines. Russia had tried, unsuccessfully, to gain access to energy resources in the same territory in a pact with Ukraine less than two years earlier.
"It's a big deal," said Carol Saivetz, a Eurasian expert in the Security Studies Program of the Massachusetts Institute of Technology. "It deprives Ukraine of the possibility of developing these resources and gives them to Russia. It makes Ukraine more vulnerable to Russian pressure."
Gilles Lericolais, the director of European and international affairs at France's state oceanographic group, called Russia's annexation of Crimea "so obvious" as a play for offshore riches.
In Moscow, a spokesman for President Vladimir Putin said there was "no connection" between the annexation and energy resources, adding that Russia did not even care about the oil and gas. "Compared to all the potential Russia has got, there was no interest there," the spokesman, Dmitry Peskov, said Saturday.
Exxon Mobil, Royal Dutch Shell and other major oil companies have already explored the Black Sea, and some petroleum analysts say its potential may rival that of the North Sea. That rush, which began in the 1970s, lifted the economies of Britain, Norway and other European states.
William Ryan, a marine geologist at the Lamont-Doherty Earth Observatory of Columbia University, said Moscow's Black Sea acquisition gave it what are potentially "the best" of that body's deep oil reserves.
Oil analysts said that mounting economic sanctions could slow Russia's exploitation of its Black and Azov Sea annexations by reducing access to Western financing and technology. But they noted that Russia had already taken over the Crimean arm of Ukraine's national gas company, instantly giving Russia exploratory gear on the Black Sea.
The global hunt for fossil fuels has increasingly gone offshore, to such places as the Atlantic Ocean off Brazil, the Gulf of Mexico and the South China Sea. Hundreds of oil rigs dot the Caspian, a few hundred miles east of the Black Sea.
Meanwhile, senior Ukrainian officials on Saturday held a second session of national "round-table" talks aimed at ending the country's political crisis, this time in the eastern city of Kharkiv, in the region that has been besieged by pro-Russian separatist violence.
The meeting brought together a broader cross-section of leaders from eastern Ukraine than the first set of talks, in an attempt to show the government's commitment to dialogue. But representatives of the region said it would be difficult to resolve the crisis until the government ended military operations aimed at suppressing the separatists.
"This is the only option in my opinion that can save Ukraine from division," said Valeriy Holenko, chairman of Luhansk Regional Council.
Leaders in Kiev are pushing to tighten Ukraine's ties with Europe, while many in the east prefer closer ties with Russia.
At times, the officials from the east disagreed strenuously with representatives of the provisional government from Kiev, highlighting still formidable differences. But Western observers said it was important that the two sides finally seemed engaged, rather than talking past each other.
The talks are largely aimed at reaching an accord on restructuring the government to increase local authority, ahead of a presidential election scheduled May 25. Kiev supports a "decentralization" plan to give more budget authority to local governments, while the pro-Russia side from the east favors a federalization model that would give more overall power to governors.