Chuck Hagel has one big hurdle left to clear before winning Senate confirmation to be the next Defense secretary — a barrage of questions on Iran, nuclear weapons and gay rights during his appearance Thursday before the Senate Armed Services Committee.

The former Republican senator from Nebraska, who has been making the rounds on Capitol Hill for weeks, will have to convince his former GOP colleagues that he supports tough policies on Iran and a focus on prevention rather than containment. A longtime arms control advocate, Hagel will also be pressed to demonstrate his support for maintaining and modernizing the military’s extensive nuclear arsenal.

In 112 pages of written answers to questions posed by the Senate Armed Services Committee, Hagel provided a preview of how he will handle those and other contentious topics, such as gay rights, during the confirmation hearing.

Criticized for being soft on Tehran, Hagel maintained in his written response to the committee that Iran should “have a path to a more prosperous and productive relationship with the international community” if it lives up to its international obligations. But, if Iran falls short, Hagel signaled that he would be hawkish.

“The other choice is clear as well — if Iran continues to flout its international obligations, it should continue to face severe and growing consequences,” Hagel wrote. “While there is time and space for diplomacy, backed by pressure, the window is closing. Iran needs to demonstrate it is prepared to negotiate seriously.”

Hagel is likely to win confirmation. But so far, among the GOP, only Sen. Thad Cochran of Mississippi, the top Republican on the Defense Appropriations Subcommittee, has committed to voting for Hagel’s confirmation.

A handful of other Republicans, including Senate Armed Services ranking member James M. Inhofe of Oklahoma, have already said they will oppose his confirmation.

Thursday’s hearing could ultimately decide how many moderate GOP senators, including Susan Collins of Maine, vote on Hagel’s confirmation.

Collins, an Armed Services Committee member until the beginning of this Congress, met with Hagel recently for 90 minutes. She characterized the meeting as in-depth and productive but says she has unanswered questions on Hagel’s thoughts on Iran sanctions in particular.

“Even though in 90 minutes I covered a lot of ground on a lot of issues, I want to hear what he says” before the Senate Armed Services Committee, Collins said earlier this week. “I’m still not happy with his views on unilateral sanctions and why he didn’t sign on to certain initiatives,” she added.

Republicans on the Armed Services Committee will likely hit Hagel on what they perceive to be inconsistencies on his stances on Iran, as well as other issues.

“Who are we getting? The guy of today or the guy who said these things before?” Sen. Lindsey Graham, R-S.C., a member of the committee, said Tuesday. Graham said he will focus his questions to Hagel on “what you said then, what you’re saying now.”

Hagel told the Lincoln Journal Star earlier this month that he has long opposed unilateral sanctions because he doesn’t believe they work and instead only isolate the United States. But in a Jan. 14 letter to California Democratic Sen. Barbara Boxer, Hagel said that “further effective sanctions, both multilateral and unilateral,” may be necessary.

In his written response to the committee, Hagel said the White House, with significant help from Congress, has brought “the world community together to confront Iran with effective sanctions.” Pressure on Iran, he added, is building.

But that likely will not be enough to satisfy some Republicans on the panel who believe Hagel has flip-flopped on the Iran issue during the confirmation process.

“Retracting your positions based solely upon public criticism of your record raises serious questions on issues that are critical to national defense,” Republican Sen. David Vitter of Louisiana wrote in a Jan. 24 letter to Hagel.

Rhode Island Democratic Sen. Jack Reed, who sits on the Armed Services Committee, defended Hagel on Wednesday, telling reporters that “historical reviews” of Hagel’s letters and votes may be interesting, but the fact remains that there are currently stringent sanctions in place.

“Hagel will be able to provide the military support to that foreign policy,” Reed said.

Republicans, meanwhile, are also expected to hit Hagel hard on his stance on nuclear weapons.

Hagel was a well-known arms control advocate during his two terms in the Senate. But it is his work after leaving the Senate — namely, a report he co-wrote last year that recommended deep reductions in the U.S. nuclear inventory and eventually retiring intercontinental ballistic missiles, which form the land leg of the military’s nuclear triad of land, sea and air delivery platforms — that has drawn the most scrutiny.

The other authors of the report, including retired Marine Corps Gen. James E. Cartwright, the former vice chairman of the Joint Chiefs of Staff, fired back this week at Hagel’s critics, stressing that they are not in favor of unilateral reductions in the U.S. nuclear inventory.

“We support bilateral, negotiated, verifiable U.S.-Russian arms reductions, to be followed by multilateral negotiations, bringing other key countries into a serious, verifiable process of reductions,” they said in a statement this week.

In his written responses to the Senate Armed Services Committee, Hagel said he supports maintaining the triad, which the military is in the early stages of modernizing.

“I support the president’s commitment to a safe, secure and effective nuclear deterrent as long as nuclear weapons exist,” he wrote. “I believe that providing necessary resources for nuclear modernization of the triad should be a national priority.”

Democrats are widely expected to support the president’s pick for the next Pentagon chief, even though many still remain noncommittal publicly.

But Hagel, who came under fire from the left for comments he made in 1998 about an ambassador nominee he called “openly, aggressively gay,” will field tough questions from Democrats about his commitment to the continued implementation to the repeal of “don’t ask, don’t tell.”

In his written responses to the committee, Hagel stressed that he fully supports the repeal of the 1993 law (PL 103-160) that banned openly gay servicemembers. He added that he would work to extend personnel benefits to the families of gay members of the military, a top priority for gay rights advocates.

“If confirmed, I will do everything possible to the extent permissible under current law to provide equal benefits to the families of all our servicemembers,” he wrote.

Democrat Tammy Baldwin of Wisconsin, the first openly gay senator, had expressed concerns about Hagel’s earlier comments. She said Tuesday that she had a “very productive meeting” with the nominee last week and “had a very positive sense at the end of it.”