WASHINGTON (Reuters) - Congress is likely to miss a Dec. 8 deadline for passing legislation funding a wide range of federal government programs through Sept. 30, 2018, kicking the contentious debate into next year, a senior U.S. House of Representatives aide said on Tuesday.

FILE PHOTO: The U.S. Capitol Building is lit at sunset in Washington, U.S., December 20, 2016. REUTERS/Joshua Roberts

With Republican and Democratic leaders in Congress still haggling over the overall level of spending for the fiscal year that began last Oct. 1, stop-gap appropriations will be needed to avert a partial government shutdown on Dec. 8 when existing funds expire, according to the aide who asked not to be identified.

The temporary funding legislation could extend at least until late January.

Failure to pass a longer-term appropriations bill before Congress breaks for Christmas sometime next month would be a setback in President Donald Trump’s drive to pump up military spending in the current fiscal year, which already is nearly two months old.

Democrats are insisting that any Pentagon spending increase be coupled with more money for an array of non-defense programs, which also have been cut or frozen under Republican austerity measures.

Without an agreement on the overall amount of spending, congressional appropriators are stymied in their ability to write a spending bill for the rest of fiscal 2018.

Earlier on Tuesday, Republican Senator Lindsey Graham, a member of the Senate Appropriations Committee, cast some doubt on Congress’ ability to pass legislation funding the government through next September, telling reporters “there probably will be a continuing resolution,” meaning a stop-gap spending bill in December.

Congress’ top four Republican and Democratic leaders were scheduled to meet Trump at the White House earlier on Tuesday to discuss government funding, tax legislation and other end-of-year measures.

But the Senate and House of Representatives Democratic leaders, Chuck Schumer and Nancy Pelosi, stayed away after Trump attacked them in a tweet as being weak on illegal immigration and driven to raise taxes. “I don’t see a deal!” Trump declared.

Schumer and Pelosi instead said they would continue their direct talks with Republican counterparts in Congress.