After nearly three years of fighting in Syria and persistent calls for a new caretaker government there, U.S. policy toward the country’s grinding civil war is tacitly acknowledging what has long been obvious: President Bashar al-Assad will remain in power, at least for a while.

The Obama administration has narrowed its policy to two main efforts: the eradication of Syria’s chemical weapons and the staging of a peace conference scheduled for this week. Both need Assad’s cooperation to succeed.

Although the official U.S. line is that Assad “must go,” the focus on striking even short-term bargains with his regime is a recognition that he retains a strong political hold.

The United States insists Assad cannot use the upcoming peace talks in Geneva to strengthen his hand, but that is just what many U.S.-backed opponents of Assad say will happen. For months, moderate opponents resisted pressure to attend the talks, seeing them as a losing proposition that would undermine their already small influence on the frontline rebels.

“They understand that this is about recognizing that Assad remains undefeated, and that no great power is willing to dislodge him as they did [Libyan leader Moammar] Qaddafi,” said Joshua M. Landis, a Syria expert and professor at the University of Oklahoma.

“The Syrian opposition does not want to go to Geneva because they understand it is tantamount to recognizing Assad will stay,” he said.

Assad has the upper hand militarily in the civil war. Despite extensive Iranian and some Russian military support, however, his forces have been unable to defeat a diverse rebel coalition that now includes large numbers of Islamist militants. The Assad government has turned that development partly in its favor by arguing that the Swiss talks will help Damascus fight terrorism.

The peace talks begin with low expectations. There is little chance that the nominal goal of a transitional government to replace Assad will emerge quickly, if ever. Analysts note that Iran will not be in attendance, further evidence that no breakthrough is in the offing.

A more realistic short-term measure of success would be temporary or localized cease-fires and freer access for humanitarian groups to needy people inside Syria.

The State Department has been quietly working toward those goals and pressuring Assad’s backers, notably Iran and Russia, to do the same. The most important goal of the conference, U.S., British and other officials said, is simply to get Assad and his opponents talking.

The war, now approaching its third anniversary, has killed more than 100,000 people and displaced many millions.

The Syrian government on Friday proposed an exchange of prisoners with rebels and a cease-fire in the largest city Aleppo, gestures that appeared designed to improve Assad’s poor image abroad ahead of the talks. U.S. and other officials said the Assad government appears ready to make further military and diplomatic concessions at what may be weeks of talks with opposition figures in Geneva.

Secretary of State John F. Kerry will help open the U.N. peace conference in the Swiss town of Montreux on Wednesday. He spent much of the past week imploring moderate political opponents of Assad to attend, although they have little pull with most of the rebels.

The main Western-backed opposition coalition said Saturday it will attend what would be the first direct negotiations between the Assad regime and its political opponents since the war began. Assad’s government had already agreed to attend.

All of the more than 30 nations attending have signed on to the goal of a transitional government, but Russia insists that Assad’s exit is not automatic. Under ground rules approved in 2012, regime and opposition figures must jointly approve members of a temporary government that would oversee what the United States calls a “political transition” — to exactly what is left intentionally vague.

Although the Assad government has scoffed at the idea that it would negotiate its own demise, Kerry said Friday the idea is not so far-fetched. He likened the bargaining process to the chemical weapons deal struck with Syria last fall.

“Nobody would have believed that Assad would have given up his chemical weapons. But he did. And the reason he did is that his patrons came to understand that he had to,” Kerry said Friday at the State Department.

“If he thinks he’s going to be part of that future,” Kerry said of Assad, “it’s not going to happen.”

The weapons agreement calls for destruction of Assad’s entire chemical arsenal this year. His government is cooperating, and the agreement relies on his continued presence to get the job done.

In the peace talks, Russia, as Assad’s main international diplomatic protector, can both lean on Assad and bolster his bona fides as the legitimate leader of Syria.

“Russia is standing on Iran’s shoulders with Syria,” said Vali Nasr, dean of the School of Advanced International Studies at Johns Hopkins University.

Although he said chances that Assad will accept a negotiated exit are slim, Nasr said any possibility of that outcome would require Russia and Iran to team up.

Humanitarian groups working inside Syria express the hope that, at a minimum, the talks will yield a timeline for a permanent cease-fire or deal to end the fighting.

“We realize we’re not going to see an immediate peaceful outcome, and that this will probably be a multi-stage process,” said Raymond C. Offenheiser, president of the U.S. branch of the hunger-relief group Oxfam, which takes no position on Assad’s legitimacy.