A key national security debate is set to kick off Tuesday as the House begins work on a $598.3 billion defense spending bill.
Two top sticking points are limits to secret surveillance programs and the push to support Syrian rebels.
Tea Party conservatives and liberal Democrats have joined forces in an unusual coalition.
They are insisting on changes that limit the authority of the National Security Agency to collect phone records of millions of Americans.
"It's not a partisan issue. It's something that cuts across the entire political spectrum," Rep. Justin Amash, R-Mich., told the House Rules Committee Monday.
They have also joined together for amendments barring the White House from arming the Syrian rebels without congressional approval.