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 Assad, U.S. 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 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 Donilon, to discuss, in part, the Syrian crisis.

The administration has been holding 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 Assad an opportunity to rally support against Israeli interference.

The White House is holding daily high-level meetings to discuss a 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 after a week of intensified fighting in Damascus, the capital, and the killing of Assad's key security aides in a bombing attack.

Administration officials insist they will not provide arms to the rebel forces. Turkey, Saudi Arabia and Qatar are financing those efforts. But U.S. officials said the United States was likely to supply some intelligence support and 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.

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, U.S. officials say they are seeking to build on and fuel the momentum of the rebels' recent battlefield successes.

Senior administration officials say the changes are in response to a series of setbacks at the U.N. Security Council, where Russia has staunchly refused to engineer the removal of 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 Tabler, a Syria expert at the Washington Institute for Near East Policy. "But like any controlled demolition, anything can go wrong."

The escalating violence has so far sent as many as 125,000 people fleeing across Syria's border into neighboring Lebanon, Jordan, Turkey and Iraq, according to the State Department.

This month, Syria started moving parts of its huge stockpile of chemical weapons out of storage, drawing stern warnings from U.S. officials not to use them or face unstated consequences.

Some U.S. intelligence officials said later that the movements were most likely a precaution as security conditions across the country rapidly deteriorated.

"It's going to take an international effort when Assad falls — and he will fall — in order to secure these weapons," Adm. William McRaven, the head of the military's Special Operations forces, told Congress in March.

U.S. and other Western intelligence officials have expressed concern that some of the more than 100 rebel formations fighting inside Syria may have ties to al-Qaida that they could exploit as security worsens in the country or after the collapse of the government.

"If the Assad regime did fall, this would provide more Islamist militants with a potential opportunity to establish a new foothold in the heart of the Middle East," said Charles Lister, an analyst with Jane's Terrorism and Insurgency Center. "The temporary lack of state structures would also afford aspirant militant Islamists with a safe area for training."