WASHINGTON — After a productive trip abroad, President Barack Obama is back in Washington, where he faces confrontations with Republicans on immigration and an oil pipeline project.

The contentious immigration debate could mean a year-end fight over keeping the government running, if some GOP lawmakers get their way.

On the foreign policy front, there is a Nov. 24 deadline in nuclear negotiations with Iran, and questions are surfacing within the administration about whether to overhaul U.S. policy toward Syria.

Given his faltering political support in the U.S. and his party’s recent election losses, Obama’s trip to China, Myanmar and Australia appeared to offer respite.

The president, who returned to the White House late Sunday, basked in policy breakthroughs with China and warm welcomes in Myanmar and Australia.

“I intend to build on that momentum when I return home,” Obama said at a news conference before heading home.

When Obama set off for the Asia-Pacific, both the White House and Republicans were suggesting that the GOP’s decisive takeover of the Senate could pave the way for bipartisan breakthroughs. But just two weeks after the election, that optimism largely has faded, making it increasingly likely that Washington will churn through two more years of gridlock.