(Adds Trump quotes, details on tentative agreement, background on dispute)
WASHINGTON, Feb 12 (Reuters) - President Donald Trump said on Tuesday he has yet to decide whether to support an agreement reached by congressional negotiators to avert another partial government shutdown that includes no funds for his promised U.S.-Mexican border wall.
But the Republican president, who triggered a 35-day closure of about a quarter of the federal government with a December demand for $5.7 billion from Congress to help build the wall, said he did not anticipate another partial shutdown.
"I have to study it. I'm not happy about it," Trump told reporters at the White House about the tentative funding deal, which would need to be passed by the Democratic-led House and Republican-controlled Senate and signed by him.
But he said another partial government shutdown appeared unlikely.
Democratic and Republican negotiators hammered out the deal on Monday night on border security provisions and money to keep several government agencies, including the Department of Homeland Security and the Justice Department, funded through Sept. 30, the end of the federal fiscal year.
Temporary funding for about a fourth of the government is due to expire on Friday.
Congressional Republicans have shown little appetite for another shutdown after taking heavy criticism over the prior one. Senate Majority Leader Mitch McConnell's comments on the Senate floor touting the agreement reached on Monday night left little doubt that the top Republican in Congress wants Trump to support it.
Top Senate Democrat Chuck Schumer was more direct, saying, "I strongly urge the president to sign this."
Trump triggered the 35-day partial government shutdown - the longest in U.S. history - with his December demand for $5.7 billion to help build the wall, which Democrats oppose.
At a rally in El Paso, Texas, on Monday night, he made clear he would not drop his quest for a wall.
Congressional sources said the agreement includes $1.37 billion for new fencing along 55 miles (90 km) of the southern border but only with currently used designs such as "steel bollard" fencing. It also addresses capacity at immigration detention facilities, specifically the number of beds for people awaiting possible deportation.
"I can't say I'm thrilled," Trump said of the agreement.
Trump added that he did not want to see another shutdown but that if there were one, it would be the Democrats' fault.
The tentative deal still requires congressional staff experts to write formal legislation, filling in details lacking in the broad outline agreed to late on Monday.
McConnell said he hopes his chamber can act on the legislation "in short order," calling the agreement "certainly good news" and saying Democrats had abandoned "unreasonable" demands.
'LOTS OF QUESTIONS'
Tom Graves, a House Republican who serves on the congressional conference committee that worked on the border security and other funding, raised questions about the compromise. Graves wrote on Twitter that he had not "signed off on the reported 'deal' nor have I seen it. Based on the reports, I have concerns. Lots of questions too."
"I am cautiously optimistic that we will get this through," Democrat Nita Lowey, who chairs the House of Representatives Appropriations Committee, told CNN. "We cannot shut the government down."
Lowey has said the legislation might be written by Wednesday, leaving little time for Congress to pass the measure by Friday's midnight deadline. Lowey said the deal had the backing of House Speaker Nancy Pelosi and other Democrats.
Trump's long-promised wall was a cornerstone of his presidential campaign. He had said it would be paid for by Mexico and not by U.S. taxpayers.
The president last month agreed to end the shutdown without getting money for a wall. The shutdown roiled financial markets and left hundreds of thousands of federal workers and contractors without pay.
Trump will have to decide whether to sign the measure into law if it is passed by Congress given its backing by congressional Republicans, or side with conservative commentators who have the president's ear such as Sean Hannity of Fox News, who late on Monday called it a "garbage compromise." While Democrats oppose the wall, they support border security efforts.
Trump has threatened to declare a "national emergency" if Congress does not provide money specifically for the wall, an action he might take to redirect other funds already provided by Congress to pay for wall construction instead. Fellow Republicans have told Trump such a step would almost certainly face a legal challenge.
"Just so you know - we're building the wall anyway," Trump said at Monday's rally in the border city of El Paso.
The number of beds in detention facilities has been a contentious part of the negotiations because it can either constrain or expand the Trump administration's ability to aggressively deport more immigrants, including those seeking asylum. Congressional aides on Tuesday gave differing accounts on the number of beds the deal permitted, with some saying it would drop to 40,520 by later this year and others saying it could rise to 58,500. Democrats had sought to limit the number.
(Reporting by Richard Cowan and Susan Cornwell; additional reporting by Doina Chiacu and Steve Holland in Washington and Roberta Rampton in El Paso, Texas; writing by Will Dunham; editing by Jonathan Oatis)