The White House on Friday called for restraint in Yemen and a peaceful transfer of power, amid reports that the country's president was wounded in a rocket attack.

"Violence cannot resolve the issues that confront Yemen, and today's events cannot be a justification for a new round of fighting," White House Press Secretary Jay Carney said in a statement.

Yemeni President Ali Abdullah Saleh was wounded when opposition tribesmen determined to topple him hammered his palace with rockets Friday in a major escalation of nearly two weeks of fighting with government forces. At least six guards were killed and eight top officials were also wounded, an official said.

The White House said the violence was "senseless" and called on all sides to cease hostilities and pursue a peaceful process of transferring power.

Saleh has agreed three times to sign onto a U.S.-backed, Gulf Arab-mediated agreement to leave power in 30 days, but each time he backed out of signing at the last minute.

Washington fears that the chaos will undermine the Yemen government's campaign against al-Qaida's branch in the country, which has attempted a number of attacks against the United States. Saleh has been a crucial U.S. ally in the anti-terror fight, but the administration is now trying to negotiate a stable exit for him.

The Pentagon said there was no move now to bring U.S. troops in Yemen out of the country.

"We do still have some service members in the country and they take necessary precautions. Beyond that, I won't talk specifics," Defense Department spokesman Col. Dave Lapan said, declining to give the number of U.S. troops there helping train local counterterrorism forces.

Lapan said there is no evidence that Yemeni forces trained by the U.S. are being used against peaceful protesters.

"We have seen reports that they have been engaged with armed forces, and are looking for more information on that aspect," Lapan told Pentagon reporters. "We still have not seen any evidence that those forces we helped train were used or have been used against unarmed protesters."

The White House said President Barack Obama's top counterterrorism aide John Brennan discussed options for addressing the deteriorating situation in Yemen during meetings with officials this week in Saudi Arabia and the United Arab Emirates. Officials from both Middle Eastern countries shared the Obama administration's deep concern about the developments in Yemen, the White House said.