Tom Barrett

A first-term House Republican facing a difficult re-election fight introduced a bill on Thursday that would authorize continued U.S. military operations in Iran through the end of July, but with strict limits, implicitly rejecting President Trump’s claim that the war has ended.

The legislation by Representative Tom Barrett, a Michigan Republican, was the latest indication of growing uneasiness among Republicans on Capitol Hill about the war, which Mr. Trump began with no authorization from Congress and which has dragged on far beyond his initial timetable. Unhappiness with the war has further darkened an already grim political environment for the G.O.P. as it grasps to keep its majorities.

Mr. Barrett, an Army veteran whose race to hold onto his Lansing-area district is considered among the most competitive in the country, said the legislation was an effort to give Congress a say in the ongoing conflict.

The bill would largely bar the introduction of ground forces and would specify how force could be used in Iran. Those uses would include to “demolish, degrade, or defeat” Iran’s nuclear program, to address “imminent threats” to American forces or facilities, to enforce a blockade of Iranian, and to ensure the safe passage of U.S. and allied ships through the Strait of Hormuz.

“The commander in chief has the sole authority to lead our troops in wartime, but I’ve lost too many friends on the battlefield to allow that to happen without Congress exercising its constitutional role to clearly define the mission with safeguards and a deadline,” Mr. Barrett said in a statement announcing the measure, which he filed during a congressional recess.