The U.S. House of Representatives returns this week for an expected political brawl over spending cuts and impeachment that could paralyze the Republican-controlled chamber, as Congress struggles to avoid a government shutdown.

The House and the Democratic-controlled Senate are due to be in session for about 12 days before funding expires on September 30, leaving little time to agree on a package of 12 appropriations bills that can pass each chamber and win U.S. Democratic President Joe Biden's signature.

The main bone of contention among House Republicans is a demand by roughly three-dozen members of the hardline House Freedom Caucus to cut spending for fiscal 2024 to $1.47 trillion, about $120 billion less than Biden and Republican House Speaker Kevin McCarthy agreed in May.

The White House and Senate leaders, including top Republican Mitch McConnell, have rejected that demand.

That dispute and other hardline demands, including opposition to Ukraine aid and calls for an impeachment inquiry against Biden, could imperil efforts to pass a short-term stopgap, known as a continuing resolution or "CR," which would keep federal agencies afloat while lawmakers debate full-scale appropriations.

"Everything's coming to a head after a long recess," Republican Representative Kelly Armstrong told Reuters, referring to the six-week-long House summer break that ends Tuesday. "We're a pretty diverse caucus, with a five-vote majority. So, threading the needle is something that's really difficult to do."

McCarthy's eight-month-old speakership could be threatened if he seeks Democratic support to avoid a shutdown or fails to move forward with an impeachment inquiry that former U.S. President Donald Trump's House allies are seeking despite a lack of votes.

Political brinkmanship over the debt ceiling has already prompted the Fitch rating agency to downgrade U.S. debt to AA+ from its top-notch AAA designation, partly because of repeated down-to-the-wire negotiations that threaten the government's ability to pay its bills.

White House spokesperson Andrew Bates warned that failure to enact $24 billion in supplemental funding for Ukraine and $16 billion for disaster-stricken U.S. communities in states including Hawaii and Florida could put lives at risk, while delaying money to combat the deadly opioid fentanyl.

(With input from Reuters)