Sen. Tim Kaine Timothy (Tim) Michael KaineBiden promises Democratic senators help in battleground states Second GOP senator to quarantine after exposure to coronavirus The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep MORE (D-Va.) on Thursday called the Obama administration hypocritical for criticizing Russia's invasion of Ukraine when it has put troops into Syria without permission.

"How can we criticize the Russian incursion into Ukrainian sovereignty when we are carrying out escalating military operations in Syria without the permission and really even against the will of the sovereign nation?" he said.

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Kaine pointed out that Russia's own military campaign in Syria is internationally legal — unlike the U.S.'s — because Syrian President Bashar Assad invited Russian forces in.

"We may think it's a bad idea, but in terms of the international legal justification for Russian activity in Syria, they've been invited in by a sovereign government," he said at a Senate Armed Services Committee hearing.

Kaine made clear he believed Russia's incursion into Ukraine was illegal and that he opposed it, but he used the comparisons to underscore his call for Congress to formally approve the U.S.'s military actions in Syria through a new authorization for use of military force (AUMF).

The Virginia senator, who is a campaign surrogate for Democratic presidential front-runner Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE, has long criticized the administration and fellow members of Congress for failing to obtain a new AUMF against ISIS.

What that failure has allowed is a "wherever and whenever" war policy, he said.

"And so at the end of this administration with the complicity of this Congress, I think we've basically come up with a war doctrine that says wherever and whenever as long as the president feels that it's a good idea without Congress even needing to do anything about it," he said.

"I think that's become the rule — that's a rule I think will haunt us — domestically under future presidents and Congresses," he added.

The administration is using the 2001 AUMF against al Qaeda to justify its actions in Syria against ISIS, arguing that the terrorist group was originally an Iraqi branch of Al Qaeda.

However, Kaine and other lawmakers have called that a stretch and say they worried about the U.S. being on perpetual war footing.

Although the administration and a handful of members of Congress, including Kaine, have proposed a new AUMF, there is broad disagreement between the administration, Democrats and Republicans over the limits it would place on military commanders executing the war.

In general, Democrats have sought to place limits on military action while Republicans say those limits could tie commanders' hands.

The administration has tried to strike a balance between both and has asserted it already has the legal authority it needs to wage the war.

Kaine said he would continue raising the issue, if only to get it on the record.

"As we breach these new milestones of escalation, I'm just going to keep putting on the record my deep concern about the precedent that we're setting for this nation ... and for other nations," he said.

Earlier this week, the administration announced the deployment of 217 additional forces to Iraq and 250 additional forces to Syria, bringing the totals up to 4,087 and 300 respectively.