As Russia continues its airstrikes against anti-Assad rebels in Syria, Martha MacCallum asked this morning what the United States should do in response. 

She talked to Sen. Marco Rubio (R-Fla.) and Fox News military analyst Gen. Jack Keane about that on "America's Newsroom."

Iranian forces are reportedly on the ground in Syria, assisting Russian forces with intelligence on where to direct their airstrikes. 

Moscow claims it's striking ISIS targets and other "extremist" groups, but U.S. officials say the bombings are aimed at moderate Syrian forces backed by the CIA. 

Rubio (video above), who predicted at the GOP debate last month that Russian airstrikes would soon begin in Syria, said President Obama took far too long to start supporting the moderate rebels. 

"By the time they got around to doing it, a lot of those people were either dead or forced into exile," said Rubio.

Rubio said the U.S. must work with Turkey to create a "safe zone" inside Syria, protected on the ground and from the air, where the rebels can organize and refugees can receive aid and shelter. He said it should have been created "months ago." 

He said Obama has no strategy and reports that the administration was caught off-guard by Putin's actions "I just shake my head."

Keane, the chairman of the Institute for the Study of War who has been briefing Congress on the issue this week, called for U.S. airstrikes against the Syrian armed forces. 

He said U.S. officials should formally warn Russia that if they continue their attacks on the American-trained rebel forces, then the Syrian military will be attacked in response.

"The first target will be the barrel-bomb helicopters. It avoids direct conflict with Russian airplanes," said Keane, adding that it's a "prudent, realistic" option to put an end to what Russia is doing.

Watch his analysis below. 

To hear more from Gen. Keane, tune in to "Fox News Sunday" at 9a ET on your local FOX network and at 2p and 6p ET on Fox News.