Obama warned to keep Congress in the loop on Syria policy

Corker said he expected the committee to be "consulted directly before you make any significant changes to the nature and scope of U.S. engagement, including providing lethal assistance to opposition forces and particularly any use of U.S. armed forces."

The letter comes amid reports that U.S. forces are helping Jordanians train rebels who could eventually create a safe zone along the border in southern Syria. In addition, a United Nations expert is poised to enter Syria to investigate claims of chemical weapons use, which Obama has called a “red line” that would spark a U.S. response.

Former Secretary of State Hillary ClintonHillary Diane Rodham ClintonBiden slams Trump over golf gif hitting Clinton Overnight Cybersecurity: Equifax hit by earlier hack | What to know about Kaspersky controversy | Officials review EU-US privacy pact Overnight Tech: Equifax hit by earlier undisclosed hack | Facebook takes heat over Russian ads | Alt-right Twitter rival may lose domain MORE and former Defense chief Leon Panetta previously recommended the United States arm the rebels. Obama has ruled against that so far out of concern that the weapons could end up in the hands of Islamist militants who could use them against U.S. interests.

Corker said he considered the administration's legal justifications for action in Libya two years ago to be “tenuous at best.” He has also expressed frustration with Secretary of State John KerryJohn Forbes KerryBringing the American election experience to Democratic Republic of the Congo Some Dems sizzle, others see their stock fall on road to 2020 The Hill's 12:30 Report MORE's recent announcement of $60 million in direct aid to the rebels, telling The Hill that he was “a little disappointed that no heads up was given.”

Corker cautioned the administration that its actions in Syria should be dictated by national security interests.

“The situation in Syria is undoubtedly dire and worsening, and I may ultimately support U.S. involvement in this case. However, our response to this evolving situation must account fully for all of our national security interests, including the risk that U.S. military involvement, limited or otherwise, could trigger escalation that might threaten our regional allies,” he said.