WASHINGTON — The Obama administration has for now abandoned efforts for a diplomatic settlement to the conflict in Syria, and instead it is increasing aid to the rebels and redoubling efforts to rally a coalition of like-minded countries to forcibly bring down the government of President Bashar al-Assad, American officials say.


Administration officials have been in talks with officials in Turkey and Israel over how to manage a Syrian government collapse. Defense Secretary Leon E. Panetta is headed to Israel in the next several days to meet with Israeli defense counterparts, following up on a visit last week by President Obama’s national security adviser Thomas E. Donilon, in part to discuss the Syrian crisis.


The White House is now holding daily high-level meetings to discuss a broad range of contingency plans — including safeguarding Syria’s vast chemical weapons arsenal and sending explicit warnings to both warring sides to avert mass atrocities — in a sign of the escalating seriousness of the Syrian crisis following a week of intensified fighting in Damascus, the capital, and the killing of Mr. Assad’s key security aides in a bombing attack.


The administration has had regular talks with the Israelis about how Israel might move to destroy Syrian weapons facilities, administration officials said. The administration is not advocating such an attack, the officials said, because of the risk that it would give Mr. Assad an opportunity to rally support against Israeli interference.


Administration officials insist they will not provide arms to the rebel forces. Turkey, Saudi Arabia and Qatar are already financing those efforts. But American officials said that the United States would provide more communications training and equipment to help improve the combat effectiveness of disparate opposition forces in their widening, sustained fight against Syrian Army troops. It’s also possible the rebels would receive some intelligence support, the officials said.


By enhancing the command-and-control of the rebel formations, largely by improving their ability to communicate with one another and their superiors and to coordinate combat operations, American officials say they are seeking to build on and fuel the momentum of the rebels’ recent battlefield successes.


“You’ll notice in the last couple of months, the opposition has been strengthened,” a senior Obama administration official said Friday. “Now we’re ready to accelerate that.” The official said that the hope was that support for the Syrian opposition from the United States, Arab governments and Turkey would tip the balance in the conflict.


Senior administration officials say the changes are in response to a series of setbacks at the United Nations Security Council, where Russia has staunchly refused to engineer the removal of Mr. Assad, as well as the turmoil that has left the Syrian government reeling, at least for the moment.


“We’re looking at the controlled demolition of the Assad regime,” said Andrew J. Tabler, a Syria expert at the Washington Institute for Near East Policy. “But like any controlled demolition, anything can go wrong.”


Mr. Obama has come under criticism from some Republican hawks, who say that the United States should intervene militarily in Syria, and from the Republican presidential aspirant Mitt Romney, who has said that he would arm the Syrian opposition — a course which the administration has not taken.


Instead, Mr. Obama had been backing United Nations efforts, and had been pushing Russia to join the United States in calling for Mr. Assad to step down from power. But Russia and China on Thursday blocked tougher United Nations action in the Security Council. This prompted Susan E. Rice, the American ambassador to the United Nations, to say that the Security Council had “utterly failed” Syria and to pledge that the United States will now instead work “with a diverse range of partners outside the Security Council” to pressure the Assad government.


Administration officials said the United States is also working with Syrian rebels to establish a transition process for the day that Mr. Assad’s government falls, including trying to set up a provisional government that would include representatives from opposing sects — Alawites, Sunnis and Christians. “We need to make sure that what comes next has Alawite representation,” one administration official said Saturday.


Outreach to the Alawite community is crucial if the Syrian state is to remain intact after Mr. Assad is gone, administration officials and foreign policy experts said. And it may be necessary to hasten Mr. Assad’s exit. “The much more urgent challenge,” said Martin S. Indyk, the former United States ambassador to Israel, “is to make contact with Assad’s generals to get them to defect with units intact.”