(Adds Senator Cornyn, Representative Collins, background)
WASHINGTON, Dec 19 (Reuters) - The U.S. Congress is in for a contentious week as infighting over defense spending, healthcare and other matters complicates the drive to pass a temporary spending bill by midnight on Friday to avert a partial government shutdown.
In a week when President Donald Trump and his fellow Republicans in Congress were celebrating their tax cut legislation, many showed little appetite for a government shutdown at week's end.
But they sounded resigned to having to navigate through at least some drama over a package that includes so many disparate components, which could make for a messy process until the end.
"I'm going to vote for whatever I need to, to keep the government open," Republican Representative Chris Collins told reporters.
Leading Republicans in the Senate and House of Representatives expressed optimism that a funding bill, coupled with a large new disaster aid package, ultimately would pass by Friday's deadline.
But some were predicting that lawmakers will bump right up against the cutoff.
The House could vote as soon as Wednesday on legislation that extends most funding for domestic programs through Jan. 19. Democrats are likely to mainly oppose the bill, arguing that their priorities were being ignored.
Conservative Republicans are insisting on higher military funding through the rest of the fiscal year ending on Sept. 30 as part of the House bill.
Democrats in the Senate are expected to block that formula if, as expected, it does not also have more money for nondefense programs.
The House measure would also include $81 billion in disaster funding to help Puerto Rico, the U.S. Virgin Islands and several U.S. states recover from hurricanes, wildfires and other natural disasters.
John Cornyn, the No. 2 Senate Republican, said senators will see whether the proposal, the largest for any single disaster aid package ever produced by Congress, is in line with their priorities. He thought the Senate is likely to maintain the $81 billion funding level.
Meanwhile, the House bill also would extend the Children's Health Insurance Program for five years.
If the Senate cuts the House's full-year funding for the Defense Department and merely extends its current levels for a few weeks, "That's a problem," said Republican Representative Jim Jordan, a member of the hard-line conservative House Freedom Caucus.
And if the Senate attaches a provision to continue federal subsidy payments for lower-income participants in the Affordable Care Act, known as Obamacare, "That's going to be a problem," said Republican Representative John Carter, a senior member of the House Appropriations Committee.
If House Democrats continue to withhold their support for the stopgap spending bill and some Republicans peel off at any stage of a complicated process, House Speaker Paul Ryan could find himself struggling to pass a bill as the clock ticks toward midnight on Friday.
The last time government agencies had to shut down because Washington could not pay its bills was in October 2013. The 17-day impasse was sparked by a failed Republican demand to withhold funding unless Obamacare was repealed. (Reporting by Richard Cowan and Susan Cornwell; Editing by Susan Thomas and Jonathan Oatis)