The letter, written by Rep. Scott Rigell, R-Va., and sent to the White House Wednesday, had been signed by 77 Republicans and 16 Democrats by midday Wednesday, Roll Call reported.
"We strongly urge you to consult and receive authorization from Congress before ordering the use of U.S. military force in Syria," the letter said. "Your responsibility to do so is prescribed in the Constitution and the War Powers Resolution of 1973."
The letter noted Obama has authority to act in emergencies but said deploying military forces in Syria "when no direct threat to the United States exists and without prior congressional authorization would violate the separation of powers that is clearly delineated in the Constitution."
"If you deem that military action in Syria is necessary, Congress can reconvene at your request," the letter said.
Republicans signing the letter include Homeland Security Committee Chairman Michael McCaul of Texas, Republican Policy Committee Chairman James Lankford of Oklahoma, Mike Simpson of Idaho, Tom Cole of Oklahoma and Tom Price of Georgia. Democrats who signed include Peter A. DeFazio of Oregon, Jim McDermott of Washington and Zoe Lofgren of California.
U.S. House Speaker John Boehner, R-Ohio, Wednesday called on Obama to "personally make the case to the American people and Congress for how potential military action will secure American national security interests, preserve America's credibility, deter the future use of chemical weapons, and, critically, be a part of our broader policy and strategy."
U.S. Sen. Rand Paul, R-Ky., called for "an open debate in Congress over whether the situation warrants U.S. involvement," since the Constitution grants Congress the power to declare war.
"The war in Syria has no clear national security connection to the United States and victory by either side will not necessarily bring in to power people friendly to the United States," he said.