Obama's administration has limited aid to nonlethal materials, like communication equipment, and officials have expressed concern about giving weapons to a disparate group of rebels of different levels of trustworthiness, saying they're concerned that some weapons would fall into the hands of terrorists.

In a speech last month at the U.N. General Assembly, Obama pledged American support for those working for a "common good" for Syria -- and sanctions against those causing harm.

"In Syria, the future must not belong to a dictator who massacres his people," he said.

"If there is a cause that cries out for protest in the world today, it is a regime that tortures children and shoots rockets at apartment buildings. And we must remain engaged to assure that what began with citizens demanding their rights does not end in a cycle of sectarian violence."

Presidential spokesman Jay Carney said Monday the White House is continuing the work to bring about leadership change in Syria.

U.N. Secretary-General Ban Ki-moon said while in France that the crisis poses a danger to Syria's neighbors, but he also urged other nations to stop providing weapons to the Syrian military or to the rebels. He expressed concern for the many refugees of the war, especially with winter approaching.