President Barack Obama has waived part of a federal law designed to prevent the supply of arms to terrorist groups so he could arm Syrian rebels.

But keeping military assistance within "vetted" opposition groups could be tricky since significant elements of the Syrian opposition are associated with radical Islamic terrorist groups including al-Qaida, The Washington Examiner reports.

The president, citing his authority under the Arms Export Control Act, announced Monday that he would waive two sections of the law that prohibit sending weaponry to countries, including Syria, that support international terrorism. The law is intended to prevent U.S. weapons from falling into the hands of countries or groups that aid or abet international terror or the proliferation of nuclear weapons and material.

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The president can waive prohibitions in the law if he "determines that the transaction is essential to the national security interests of the United States."

Under the law, the White House must also provide Congress, at least 15 days before turning over the weapons, with details including the name of any country involved, the identity of the recipients, the purpose of the weapons, an inventory of the arms being delivered, and an statement that the transfer is key to American security interests.

The administration has bipartisan support in its efforts to provide military assistance to the Syrian opposition. Both GOP Sen. Bob Corker of Tennessee and Democrat Sen. Carl Levin of Michigan have endorsed Obama's plans.

"Our intelligence agencies, have a very good handle on who to support and who not to support," Corker said. "And there's going to be mistakes. We understand some people are going to get arms that should not be getting arms. But we still should be doing everything we can to support the free Syrian opposition."

Obama's decision came on the same day that details of a report from defense analysts IHS Jane's were released saying nearly half those fighting against President Bashar Assad's Damascus regime are hardline Islamists.