A U.S. drone fired on two senior commanders of Somalia's Shebab Islamist insurgency after they were found to have ties to al-Qaida, the Washington Post reported late Wednesday, citing U.S. officials.

The strike last week is believed to have wounded the two leading militants and came amid increasing concern among U.S. officials about growing ties between Shebab and the global terror network, the Post said.

Iran and Syria "remain leading state sponsors of terrorism," top U.S. counterterrorism official John Brennan said on Wednesday while introducing a new American anti-terrorism strategy.

"Hezbollah and Hamas are terrorist organizations that threaten Israel and our interests in the Middle East. We will therefore continue to use the full range of our foreign policy tools to prevent these regimes and terrorist organizations from endangering our national security," Brennan said.

Washington said Wednesday it was setting sanctions on Syria's Political Security Directorate for human rights abuses, citing two incidents when its agents shot down protesters in March and April.

Also named in the sanctions were the country's air force intelligence chief, Major General Jamil Hassan, and Iran's national police for "providing support to the Syrian regime."

Pakistan told the United States to leave a remote desert air base reportedly used as a hub for covert CIA drone attacks, Defense Minister Ahmed Mukhtar was quoted by state media as saying Wednesday.

His remarks are the latest indication of Pakistan attempting to limit U.S. activities since a clandestine American military raid killed Osama bin Laden on May 2 and plunged ties between the anti-terror allies into chaos.

The Syrian regime's authorization of an opposition meeting is a "move in the right direction," but President Bashar al-Assad still needs to go further, the United States said Tuesday.

About 160 dissidents, several of whom have spent years in jail as political prisoners, gathered Monday, prompting the U.S. State Department to say it was "pleased to see the opposition has been allowed some breathing space."

The top U.S. military nuclear research lab was ordered to stay closed Tuesday after flames reached it and the local town began evacuating, though all high-risk materials were safe, officials said Monday.

The Los Alamos National Laboratory (LANL) said there had been "no off-site releases of contamination" after a one-acre (.40 ha) blaze on the southwestern edge of the research complex northwest of Santa Fe, New Mexico.

A U.S. lawmaker strongly opposed to U.S. military involvement in Afghanistan and the Libyan conflict is on a "fact-finding" visit to Lebanon and Syria, his office said Monday.

Democratic Representative Dennis Kucinich held talks Monday in Damascus with Syrian President Bashar al-Assad, Syria’s state news agency SANA reported.

The United States termed as "significant" a Syrian opposition meeting in Damascus where around 160 activists called for democracy and a peaceful end to the regime of President Bashar al-Assad.

"This is a significant event," U.S. State Department spokeswoman Victoria Nuland told reporters.

In a symbolic but scathing rebuke to President Barack Obama, the U.S. House of Representatives on Friday rejected a resolution authorizing U.S. military action in Libya for one year.

Lawmakers defeated the measure with 295 voting against and only 123 for, and moved to take up a companion resolution aimed at sharply reducing the U.S. role in NATO-led, U.N.-mandated operations against Libyan strongman Moammar Gadhafi's forces.

The United States said Friday it was monitoring Venezuela's ties to Iran and "no option" is off the table for potential sanctions against President Hugo Chavez's government in Caracas.

Kevin Whitaker, the acting deputy assistant secretary for Western Hemisphere affairs, said Washington was monitoring Venezuela for "patterns of support for acts of international terrorism."