WASHINGTON  The nation’s top two defense officials called Tuesday for an end to the 16-year-old “don’t ask, don’t tell” law, a major step toward allowing openly gay men and women to serve in the United States military for the first time.

“No matter how I look at the issue, I cannot escape being troubled by the fact that we have in place a policy which forces young men and women to lie about who they are in order to defend their fellow citizens,” Adm. Mike Mullen, the chairman of the Joint Chiefs of Staff, told the Senate Armed Services Committee.

As a murmur swept through a hearing room packed with gay rights leaders, Admiral Mullen said it was his personal belief that “allowing gays and lesbians to serve openly would be the right thing to do.”

He is the first sitting chairman of the Joint Chiefs to support a repeal of the policy, and his forceful expression of his views seemed to catch not only gay rights leaders but also Senator Carl Levin, the Michigan Democrat who is the committee’s chairman, by surprise.