In the seven years since Sen. Tim Kaine (D-Va.) took office, he has been obsessed with curbing presidents’ efforts to deploy the military without congressional say-so — decrying the use of resolutions from 2001 and 2002 to justify sending troops into harm’s way years later.

Now that the killing of Iranian military commander Maj. Gen. Qasem Soleimani has increased tensions with Iran, Kaine is approaching the issue from another angle and starting to gain traction.

Kaine last week introduced a war powers resolution that would “remove United States Armed Forces from hostilities against the Islamic Republic of Iran or any part of its government or military,” an attempt, he said, to prevent further escalation in the region.

A similar measure was quickly proposed in the Democratic-majority House, introduced by Rep. Elissa Slotkin (D-Mich.), a former CIA and Pentagon analyst, and passed Thursday afternoon on a mostly party-line vote.

Kaine, a member of the Armed Services and Foreign Relations committees, has spent the last week talking up his resolution and trying to bring Republicans on board.

He got a major break Wednesday when Republican Sens. Mike Lee (Utah) and Rand Paul (Ky.) told reporters they’d back his effort. Since then, Kaine said, he has spoken with eight or nine more senators from the 53-member GOP caucus, with more meetings planned.

He needs 51 votes for the resolution to pass. A vote could come as soon as Tuesday. Kaine said he has agreed to remove references to President Trump from the resolution — it would, of course, apply to all presidents — and to make other technical changes.

“It doesn’t mean everyone I talk to will get on board,” Kaine said in an interview. “But me sitting down with them and talking them through why I’ve done it this way, it gives them some level of comfort.”

Although Trump has not reacted to Kaine’s resolution, on Thursday morning the president tweeted, in part: “Hope that all House Republicans will vote against Crazy Nancy Pelosi’s War Powers Resolution.”

Kaine on Friday plans to talk to Junior Reserve Officers’ Training Corps cadets at an Alexandria high school about his efforts to more clearly define the roles of Congress and the president in deploying service members.

“When we ask our troops to risk everything, we in Congress cannot hide under our desks, outsource our constitutional duty to the president, and pretend that we can avoid accountability for war and its consequences,” he wrote in a Wednesday op-ed published by Fox News.

The issue is vital to Kaine both as a senator — his state has among the most active and retired military personnel — and a father. His son is an active-duty Marine.

For years, he has tried to repeal and replace post-9/11 authorizations Congress passed in 2001 and 2002 as a legal basis for military action in Iraq and Afghanistan. Kaine says the legislation has been inappropriately stretched to justify U.S. military engagements well beyond the original authorization and that Congress has abdicated its responsibility for declaring war under the Constitution.

The United States used the 2001 authorization in dozens of instances to send forces to nations including Libya, Turkey, Georgia, Syria, Iraq, Afghanistan, Yemen, Eritrea, Ethiopia, Djibouti, Somalia, Kenya, the Philippines and Cuba.

A new Authorization for Use of Military Force, Kaine argues, would show troops risking their lives that Congress has made a fresh determination that their mission is in the national interest.

Kaine considered it a modest victory for his cause in December 2018, when 14 Senate Republicans joined Democrats in voting to end U.S. military support for the Saudi-led coalition fighting in Yemen. Trump ultimately vetoed the measure but stopped refueling Saudi bombing jets on the way to Yemen.

Three Republicans who were key allies on the issue are no longer in the chamber: senators Bob Corker (R-Tenn.), then chairman of the Foreign Relations Committee, and Jeff Flake (R-Ariz.) have left Congress, and senator John McCain (R-Ariz.) died.

Kaine also won majority support for a June 2019 amendment to the defense spending bill that would have prohibited defense funds from being used for a war with Iran. But he could not muster the 60 votes needed to pass the measure.

His efforts began during the administration of former president Barack Obama, whom he describes as a friend. Kaine unsuccessfully pressed Obama to seek permission from Congress before committing U.S. forces to the conflicts in Libya and Syria, and the war against the Islamic State.

With the transition to a new administration, Kaine said, his worry about the potential abuse of power grew.

“For years, I’ve been deeply concerned about President Trump stumbling into a war with Iran,” he said. “We’re now at a boiling point, and Congress must step in before Trump puts even more of our troops in harm’s way.”

Karoun Demirjian contributed to this report.