Sen. Tim Kaine (D-Va.) warned this week that the Obama administration must seek out congressional authority for any military action against the Islamic State, and also called on officials to develop a full strategy for engagement against the terrorist group before acting.

“I agree that ISIL poses a significant terrorist threat to U.S. interests and partners in the region, which is why the administration has initiated military action against the group,” Kaine said. “But I do not believe that our expanded military operations against ISIL are covered under existing authorizations from Congress.”

President Barack Obama is being urged by a Senate Democrat to seek congressional authorization to fight the Islamic State, and to come up with a clear plan for dealing with the terrorist group. (AP Photo/Chuck Burton)

Kaine said that while the Constitution lets the president deal with imminent threats to the U.S., “I have reservations regarding whether our military actions against ISIL all meet this test.”

Kaine’s comments, and similar remarks from other senators, put new pressure on the Obama administration as it weighs its choices for dealing with the Islamic State, also known as ISIL or ISIS. The public execution of a U.S. photojournalist has led to calls for the U.S. to aggressively strike the group before it consolidates more power, land and influence in Syria and Iraq.

President Barack Obama has said for the last few weeks that he wants to avoid committing U.S. ground troops to the region. But after the beheading of James Foley, even Obama said the U.S. would be “relentless” in brining Foley’s killers to justice, and officials have lately said the terror group poses a significant threat to U.S. security.

The administration has signaled that it would seek congressional authority before committing ground troops, and Kaine said he is “encouraged” by that. But Kaine also said that Congress needs to be involved in order to formulate an agreed-upon strategy that can be used to fight what most agree is a terrorist group that must be brought to heel.

“This fight, and the threat posed by ISIL, is serious enough that Congress and the Administration must be united on U.S. policy going forward,” he said. “I urge the administration to use the next two weeks to clearly define the strategy and objectives of its mission against ISIL, then bring it to Congress for a debate and authorization vote.”