In the last month alone, the White House gave the C.I.A. and the military broader authority to carry out drone strikes in Yemen. The policy shift allows strikes against militants who may be plotting attacks against the United States but whose identities might not be fully known, an authority that already exists in Pakistan. Previously, America focused on a list of known leaders of the Qaeda affiliate in Yemen.

In yet another indication of the United States’ concern, two senior military officials said that the Pentagon was dispatching dozens of military trainers to Yemen, resuming a program for the country’s counterterrorism forces that was suspended last year when many troops abandoned their posts or were summoned to Sana, the capital, to help support the tottering Saleh government.

The United States mounted a manhunt for Mr. Quso after he was indicted in Federal District Court in the Southern District of New York in the Cole bombing on Oct. 12, 2000. American officials said Mr. Quso had planned to tape the bombing from a hill above the harbor of Aden, where the destroyer was docked, and to use the tape to recruit terrorists. It was not clear whether such a tape was made.

Mr. Quso, who escaped from a jail in Yemen in 2003, was trained in terrorist camps in Afghanistan. “He’s certainly a significant figure, but he’s not at the very top of Al Qaeda in Yemen,” Gregory Johnsen, a Princeton scholar who closely tracks militants in Yemen, said in a telephone interview.

A spokesman for Ansar al-Sharia, a Qaeda-linked group in south Yemen, confirmed Mr. Quso’s death in a phone interview, and said that an American drone had carried out the strike. The spokesman, who goes by the name Abu Hajer, said that one other man was killed in the attack. Reuters reported that the two men were traveling by car when they died.

Militants from Al Qaeda in the Arabian Peninsula started to use the name Ansar al-Sharia last year when the group began to take over territory in Yemen’s south while the government was preoccupied with a political crisis in Sana. The breadth of the connection between Ansar al-Sharia and the main Al Qaeda leadership in Pakistan is disputed.