Updated

The Obama administration’s effort Sunday to win support for a punitive military strike on Syria is facing opposition and criticism in part because of its handling of the fatal Benghazi terror attacks, which occurred one year ago Wednesday.

Federal prosecutors last month filed the first criminal charges related to the Sept. 11, 2012, attacks on the U.S. outpost in Benghazi, Libya, in which four Americans were killed.

The sealed charges are against Libyan militia leader Ahmed Abu Khattalah. Though he has given interviews with several major news outlets, Khattalah has not been taken into custody. And others seen with Khattalah in videos from the outpost’s security cameras also have not been found by authorities.

“We've been very clear that we will hold those people who carried out this dastardly, heinous attack against our people to account," White House Chief of Staff Denis McDonough told “Fox News Sunday.” “You know what the United States does? We track every lead until we ...can accomplish what we say we will do."

Other issues related to the 2012 attack in which U.S. Ambassador Chris Stevens and three other Americans were killed included whether the administration was up-front with Americans about intelligence reports. Officials said at first that the attacks appeared to be in response to an anti-Islamic video, then acknowledged they were terror related.

“When it happened, [President Obama] promised to hunt down the wrong-doers,” Texas Republican Sen. Ted Cruz said on ABC’s “This Week.” “Yet a few months later, the issue has disappeared. You don't hear the president mention Benghazi. Now it's a phony scandal. We ought to be defending U.S. national security and going after radical Islamic terrorists.”

Now administration officials are trying to convince Americans and Capitol Hill lawmakers that Syrian President Bashar Assad ordered an Aug. 21 attack on his own people and his forces used the deadly nerve gas sarin. Nearly 1,500 of Assad’s own people were killed in the attack.

World leaders are also skeptical enough about the administration’s claims about the attack to wait for the findings of a United Nations’ investigation before backing a military strike.

In July, Capitol Hill Republicans sent a letter to new FBI Director James Comey urging him to take action.

"It has been more than 10 months since the attacks," states the letter, spearheaded by South Carolina Sen. Lindsey Graham and Utah Rep. Jason Chaffetz. "We appear to be no closer to knowing who was responsible today than we were in the early weeks following the attack. This is simply unacceptable.”