Yemen's president says he's ready to step down at the end of the year in an orderly transfer of power.

Ali Abdullah Saleh told senior officials and military commanders of his decision on Monday. But he vowed not to hand power to military commanders who have joined the opposition in defections that he branded as an attempted coup, a spokesman said Tuesday.

There has been no response from the opposition, but powerful clergy, tribal leaders and army commanders are now calling for Saleh to step down.

The announcement came after Saleh's forces opened fire on demonstrators on March 19 killing 40 people as the protested in the capital square.

The killings prompted three senior military officers to join the opposition.

Three ministers and dozens of members of parliament also quit Saleh's regime in response to the massacre.

Presidential spokesman Ahmed al-Sufi told The Associated Press that Saleh met with senior Yemeni officials, military commanders and tribal leaders Monday night and vowed not to hand power to the military. He said the Monday defection of military commanders including longtime confidante Maj. Gen. Ali Mohsen al-Ahmar was a "mutiny and a coup against constitutional legitimacy."

"I don't wish and will not accept the transfer of power to the military," al-Sufi quoted Saleh as saying. "The military institution remains united. The era of coups is gone."

U.S. State Department spokesman Mark Toner called on the Yemeni leader to refrain from violence.

"We abhor the violence. We want a cessation of all violence against demonstrators," Toner said, calling on Saleh to "take the necessary steps to promote a meaningful dialogue that addresses the concerns of his people."