(Adds Senate delay on bill, Flint water assistance)
By Richard Cowan
WASHINGTON, Dec 8 (Reuters) - The U.S. House of Representatives on Thursday overwhelmingly passed legislation to keep federal agencies funded until April 28 and avert government shutdowns at the end of this week when existing appropriations expire.
By a vote of 326-96, the House passed the legislation that is now before the Senate where it has encountered opposition from Democrats who are upset over the refusal by Republicans to include a long-term extension of expiring healthcare benefits for retired coal miners and their families.
Instead, the bill would continue the benefits only until next April.
"I've never seen anything this callous in my life," said West Virginia Democratic Senator Joe Manchin.
As a result, the Senate might not be able to vote on the spending bill until sometime this weekend, technically putting the U.S. government into a partial shutdown mode on Saturday.
Flint, Michigan, which has endured a two-and-a-half-year struggle with lead-contaminated drinking water, would get access to a $170 million fund for infrastructure improvements and lead poisoning prevention under the bill.
The stop-gap funding bill reflects the inability of the Republican-controlled Congress to pass the dozen regular appropriations bills for the fiscal year that began Oct. 1 and runs through Sept. 30, 2017, freezing most spending at current levels.
Congress was unable to pass them in part because of internal disagreements among Republicans on some of those measures and because Democrats held firm to an earlier budget deal that aims to restrain spending caps on defense as long as those caps were imposed on other domestic programs.
Congress likely will end up arguing well into 2017 over spending priorities for the current fiscal year even as it must begin considering funding government operations in fiscal 2018.
Congress' delay in finishing its work also means that President-elect Donald Trump, who takes office on Jan. 20, will have some say in government spending priorities for the period of April 28-Sept. 30, instead of President Barack Obama.
A provision is also embedded in the spending bill to make it easier for Trump to win confirmation of General James Mattis to be defense secretary early next year. Republicans demanded it to help Mattis get around a requirement that the defense secretary be a civilian for seven years before taking the job. Mattis retired from the military in 2013.
The bill moving through Congress, as lawmakers try wrapping up their work for the year, contains $5.8 billion for waging military operations against the Islamic State worldwide. (Reporting By Richard Cowan; Editing by Chris Reese and Alan Crosby)