"If we keep this hands-off approach to Syria -- this indecisive action toward Syria, kind of not knowing what we're going to do next -- we're going to have a war with Iran because Iran's going to take our inaction in Syria as meaning we're not serious about their nuclear weapons program," Senate Armed Services Committee member Lindsey Graham, R-S.C., told the CBS News program "Face the Nation."
"We need to get involved," he said, saying there was "a growing consensus" in the Senate for U.S. military involvement.
Graham and other GOP lawmakers -- in appearances on the Sunday U.S. TV talk shows -- sought to pressure the Obama administration, three days after the White House said in a letter to congressional leaders U.S. intelligence agencies assessed "with varying degrees of confidence" the Assad regime used the chemical agent sarin on a small scale against his own people.
President Barack Obama previously said the use of chemical weapons in Syria would be a "red line" that would set off a U.S. response.
Obama said Friday, a day after the letter's release, the disclosure was "a game changer."
But he said he had not yet seen "confirmation and strong evidence" chemical weapons have been used.
"What we have right now is an intelligence assessment," Obama told reporters, adding Washington was working with allies "to obtain more direct evidence."
The White House says it wants to establish who used the weapons, and whether their use was deliberate or accidental, before deciding whether a red line has been crossed and U.S. action is warranted.
"There's nothing you can do in Syria without risk," Graham told "Face the Nation." "But the greatest risk is a failed state, with chemical weapons falling in the hands of radical Islamists, and they're pouring into Syria. The longer this goes, the more likely you have a failed state, and all hell's going to break loose in the region.
"It's a disaster for the region. It's going to be a disaster for the world," he said.
"One way you can stop the Syrian air force from flying is to bomb the Syrian airbases with cruise missiles. You don't need to go deep into Syria to do that," Graham said.
This would "neutralize the air advantage the Syrian government has over the rebels," he said.
Armed Services Committee member John McCain, R-Ariz. -- one of two senators requesting the White House letter on chemical weapons -- told NBC's "Meet the Press" the United States could attack Syrian air bases with missiles but should not send in ground troops.
"The worst thing the United States could do right now is put boots on the ground in Syria," McCain said. "That would turn the people against us."
He said Syrian refugees were already angry at the United States for its inaction.
"I don't think we're at that point right now, but we're close," he said. "But the fact is, for America to sit on the sidelines and do nothing is a huge mistake because the world is watching."
House Intelligence Committee Chairman Mike Rogers, R-Mich., said lawmakers had classified information indicating the regime of President Bashar Assad was using chemical weapons for the past two years.
"The problem is, you know, the president has laid down the line," Rogers said. "And it can't be a dotted line. It can't be anything other than a red line. And more than just Syria, Iran is paying attention to this. North Korea is paying attention to this."
Sen. Claire McCaskill, D-Mo., said the administration should increase its humanitarian aid to Syrians who fled the fighting. But she refused to rule out military action.
"I don't think you want to ever rule it out," she told "Face the Nation."
She said she would not support sending U.S. ground troops into Syria "unless it's absolutely necessary."
"If we take the bomber action, then that may lead to something else, and that's really what I'm referring to in terms of you don't ever want to say absolutely never any boots on the ground because, you know, Iran is busy here. Iran is very busy here. And so is Hezbollah," McCaskill said. "So it's just one of those things that we've got -- I think that we do need to be very cautious."
Rep. Keith Ellison, D-Minn., like McCaskill, focused on stepping up humanitarian assistance to Syrian refugees.
"I believe the United States could play a greater role in dealing with the humanitarian crisis," Ellison said on "Meet the Press" -- something McCain also called for on the program.
"We have spillage and refugees in Jordan, in Lebanon and currently displaced people in Syria," he said. "The suffering is intense. And I don't think the world's greatest superpower, the United States, can stand by and not do anything."