Sen. Tim Kaine, D-Va., said he believes he is "close" to securing enough GOP support to pass a war powers resolution directing President Donald Trump to withdraw U.S. forces from Iran.

Kaine told The Hill that Democrats are optimistic they can attract a fifth Republican vote to pass legislation aimed at ending U.S. military involvement in the conflict, which has stretched into its 15th week.

"We think we can have a narrow win," Kaine said. "I don't have one absolutely pinned down, but I think I'm close."

The resolution would invoke the 1973 War Powers Act, which requires congressional authorization for prolonged military engagements.

Kaine and fellow Democrats argue that Congress should have a greater role in deciding whether the United States remains involved in hostilities with Iran.

Four Republican senators have already voted to move the measure out of the Senate Foreign Relations Committee, including Sen. Rand Paul, R-Ky.; Sen. Susan Collins, R-Maine; Sen. Lisa Murkowski, R-Alaska; and Sen. Bill Cassidy, R-La.

But despite Democrat optimism, the proposal still faces significant hurdles.

Even if the Senate approves the measure, it would need to pass the Republican-controlled House and overcome an almost certain presidential veto.

Under the Constitution, Congress would need two-thirds majorities in both chambers to override Trump.

Many Republicans remain firmly behind the president's strategy.

Sen. John Cornyn, R-Texas, argued that now is not the time to ease pressure on Tehran.

"I want President Trump to finish the job," Cornyn told The Hill. "I'm very dubious about any agreement that you'd get with this radical regime because they won't abide by it."

Cornyn warned that Iran cannot be trusted to honor agreements and said the regime should not be left with leverage over the Strait of Hormuz or access to enriched uranium that could be used to revive a nuclear weapons program.

Other Republicans have also dismissed the resolution as political theater.

Sen. Todd Young, R-Ind., argued that supporters have failed to explain what would happen if U.S. forces abruptly withdrew.

"All I can think of are the dangers associated with immediate withdrawal," Young said.

Congress has increasingly debated its constitutional role in authorizing military force as the conflict has continued beyond the 60-day threshold outlined in the War Powers Act.

However, critics of the resolutions argue they risk undermining the commander in chief during an ongoing international crisis.

The debate comes as Trump has intensified pressure on Iran, warning Tehran that it will "pay the price" for delaying negotiations while continuing military and economic operations designed to curb the regime's influence in the region.

For now, Democrats may be gaining support, but Trump's Iran policy still enjoys significant backing among Republicans who believe sustained pressure is the best path to protecting American interests and preventing Iran from obtaining a nuclear weapon.

Reuters contributed to this report.