(Adds Trump to sign back-pay legislation in paragraph 5)
By Steve Holland and David Morgan
WASHINGTON, Jan 15 (Reuters) - The U.S. economy is taking a larger-than-expected hit from the partial government shutdown, White House estimates showed on Tuesday, as contractors and even the Coast Guard go without pay and talks to end the impasse seemed stalled.
The longest such shutdown in U.S. history dragged into its 25th day with neither President Donald Trump nor Democratic congressional leaders showing signs of bending on the topic that triggered it - funding for a wall Trump promised to build along the border with Mexico.
Trump insists Congress shell out $5.7 billion for wall funding this year, as about 800,000 federal workers go unpaid during the partial shutdown. He has refused to support legislation providing money for a range of agencies to operate until he gets the wall funds.
With the shutdown dragging on, federal courts will run out of operating funds on Jan. 25 and face "serious disruptions" if the shutdown continues, according to a court statement.
To try to take some of the sting out of the shutdown, Trump planned to sign on Wednesday the “Government Employee Fair Treatment Act of 2019," which is legislation that would ensure that those federal workers furloughed will receive backpay once the shutdown is over.
The Internal Revenue Service said it planned to bring more than 46,000 furloughed workers back to their jobs as the agency enters its peak season of processing tax returns and refunds.
Trump invited a bipartisan group of lawmakers for lunch to discuss the standoff, but the White House said Democrats turned down the invitation. Nine House of Representatives Republicans, none of whom are involved in party leadership, attended.
One attendee, John Katko, told CNN that Trump "wanted to continue to engage in negotiations." He did not mention any new proposals Trump might pursue.
House Democratic leaders said they did not tell members to boycott Trump's lunch but had pressed those invited to consider whether the talks would be merely a photo-op for Trump.
Separately, a bipartisan group of senators explored solutions. Senator Lisa Murkowski, a Republican participant, told reporters in a Capitol hallway that the group had “momentum,” but gave no details.
Senator Joe Manchin, a Democratic participant, said: "Anything can be part of the negotiations."
Lawmakers were supposed to be in their districts and states next week after Monday's Martin Luther King Jr. holiday, but the House and Senate planned to cancel the recess if the shutdown persists.