CINCINNATI, Ohio (WTVN) -- The United States must respond to Syria's use of chemical weapons, according to U.S. Sen. Rob Portman. The Ohio Republican says that the country's credibility is on the line.

"We have to hold them accountable. Assad seems to want to thumb his nose at the international community, we've got to make sure that we respond," he said.

President Obama called use of chemical weapons "crossing the red line." Portman says not taking action makes future threats from America worthless.

"I do not support the United States intervening in the civil war. I certainly don't support boots on the ground. What I do support is a limited strike so long as it is targeted and so long as it is multi-lateral meaning that we have allies with us," he said.

Whatever the U.S. does, Portman doesn't think it should rely on backing from the United Nations because Russia will likely block it. Portman says there is support for military action from NATO as well as members of the Arab League.

Portman points out that the Obama Administration promised to bring the people responsible for the attack on the U.S. Embassy in Libya as well, but so far that hasn't happened.

"I do think the United States under the Obama Administration has not followed through when they draw red lines," Portman said.

Ohio's other U.S. Senator, Democrat Sherrod Brown, wasn't available for an interview, but his office did issue a statement saying that President Obama needs to make his case for taking action in Syria to the American people and consult with Congress.

"The U.S. must work with our allies to ensure security in the region and an end to violence. We need an international approach to ending the humanitarian crisis in Syria and ensuring stability and peace in the region," Brown said.

Brown says the regime in Syria has killed, detained, and tortured civilians.

(Photo courtesy Getty Images)