WASHINGTON, Sept. 19 (Xinhua) -- The Obama administration said on Friday that it would take months to vet and train Syrian rebels to make them ready for battle against the Islamic State (IS) fighters.

　　National Security Adviser Susan Rice said the administration will move as fast as it "reasonably can" after Congress approved President Barack Obama's plan to train and arm vetted Syrian rebels.

　　"But this is something that will take many months," she said at a White House daily news briefing.

　　"It is not something that one should expect will yield rapid and immediate fruit," Rice said, adding, "This is a serious training program, and we're serious about vetting those that we will be training and equipping."

　　Rice, however, refused to say when Obama would give the go- ahead to the new air campaign in Syria, 10 days after the president said he had authorized U.S. air strikes against Islamic State targets in Syria.

　　Also on Friday, the Pentagon detailed the training program in Syria that will focus on three things: defending their communities, going after the IS forces, and taking on the Assad regime.

　　It is going to take "probably three to five months" before the vetting process is complete, Pentagon Press Secretary John Kirby said at a news conference. "Then there will be probably a period of eight to 12 months of actual training and fielding."

　　As Washington moved forward with its training program which aims to involve about 5,000 what it calls "moderate" Syrian rebels, an international battle is also taking shape. More than 40 countries have agreed to join the coalition fighting IS militants who have seized large parts of Iraq and Syria, Kirby said.

　　Saudi Arabia will host the training camp in an already established facility, the admiral said. "We're grateful for that .. . Now, we're going to move forward on getting that train and equip mission up."

　　Since Aug. 8, U.S. fighter aircraft have so far conducted a total of 178 airstrikes across Iraq. The airstrikes have effectively slowed the advances of IS fighters, but U.S. Army Chief of Staff Ray Odierno cautioned that airstrikes alone will not defeat the extremist group.

　　"You need a complementary ground capability that will go in and do that," he said, referring to a strategy relying on partner forces on the ground to support air raids carried out by U.S. warplanes.

　　These boots on the ground will be moderates in Syria and Iraq, as well as troops from other Arab nations who would like to assist, he said, adding that the U.S. will train, equip and advise them as needed.

　　"We all agree with the current strategy we're executing," he said. "We've got to give this time to work. It's important they're the ones who will defeat ISIL."

　　Meanwhile, Odierno cautioned that targets will become more difficult in the future as the extremists blend in with the civilian population and possibly use them as human shields.