LONDON -- Secretary of State Hillary Rodham Clinton bluntly warned Yemen's leaders Wednesday to "take ownership" of their own long-festering problems -- corruption, internal strife and poor governance -- if they hope to overcome threats from violent extremism and poverty.

Ms. Clinton's comments reflected the impatience of the Obama administration as it once again faces a dire security threat from a country whose government is marred by corruption and incompetence, like those in Afghanistan and Pakistan.

"Yemen must take ownership of the challenges it faces, and of its internal affairs," Ms. Clinton said at a 20-nation meeting the British government convened to reinvigorate world efforts in a terrorist hot spot. The conference came as the Yemeni terrorist threat has been thrust under a world spotlight by the failed attempt of al-Qaida's Yemen affiliate to blow up an airliner over Detroit on Christmas Day.

Ms. Clinton noted that only four years ago, world powers pledged $5.2 billion to help the impoverished country. But only a small fraction of that has been delivered, she said, partly because of donors' concerns that it would not be spent as intended. If international support is to continue, Yemen "must demonstrate that it can allocate foreign aid effectively," she said, including by improvements in security and government shortcomings that discourage investment.

Ms. Clinton said she was encouraged by the Yemeni government's efforts against terrorism, and by its plans for economic and political reform. But, in a reference to past reform pledges that did not materialize, she said the promises "will not mean much" if they are not implemented.

"Some might ask," she said, "given the past history, why we should feel compelled to offer more assistance to Yemen. The answer is that we cannot afford inaction."

The Obama administration is stepping up military and intelligence cooperation with Yemen to combat militants, but also is expanding economic and development aid to counter root causes of the country's dysfunction.

The government of longtime President Ali Abdullah Saleh has been struggling with a rebellion of the Shiite Houthi tribesmen in the north, and secessionist forces in the country's south, at a time when Islamist extremists have been flocking to ungoverned sections of the country.

Saudi Arabia announced Wednesday that nearly three months of fighting between Saudi troops and Shiite Muslim rebels along the Yemen border had ended, declaring victory two days after the rebels offered a cease-fire.

Saudi forces and warplanes have pounded Houthi militants since the rebels killed a Saudi border guard and infiltrated villages in early November. The fighting, which led to fears of wider regional chaos, drew the Saudis into the sporadic 5-year-old conflict between the insurgents and Yemen's government.

There has been no official cease-fire, and it was unclear if fighting would resume in mountains where the rebels continue to battle Yemeni forces. The Houthis had attacked Saudi positions along the border after accusing the kingdom of helping Yemen try to crush a rebellion that since 2004 has killed hundreds and forced 200,000 to flee their homes.

Rebel leader Abdul-Malik Houthi proposed a cease-fire Monday, saying his movement wished "to avoid more bloodshed and to stop aggression on civilians." Speaking to reporters Wednesday, Prince Khaled bin Sultan, the deputy defense minister, said the Saudis had won a "clear victory," and that the rebels were forced back into Yemen.

Yemen is in a downward spiral economically, with both its water and oil reserves dwindling and its population of 23 million exploding.

A senior State Department official one of Ms. Clinton's chief goals in the meeting was to urge Yemen to seek a cease-fire with the Houthi rebels.

But in a joint news conference after the meeting, Yemeni Foreign Minister Abu Bakr al-Qirbi resisted U.S. pressure for a cease-fire, which would be his government's sixth in five years.

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