Declaring that members of the military will no longer be asked to lie, President Barack Obama fulfilled a campaign promise Wednesday and signed a landmark law repealing the ban on gay men and women serving openly in the armed services.

"This is a good day," a beaming Obama said. "This is a very good day."

The new law ends the 17-year-old "don't ask, don't tell" policy that forced gays to hide their sexual orientation or face dismissal. Its repeal comes as public opinion on such issues as gay marriage and gay rights in general has grown more tolerant.

"I say to all Americans, gay or straight, who want nothing more than to defend this country in uniform, your country needs you, your country wants you, and we will be honored to welcome you into the ranks of the finest military the world has ever known," Obama said.

The service chiefs must first complete implementation plans before lifting the old policy — and they must certify to lawmakers that it won't damage combat readiness, as critics charge. But Obama said: "We are not going to be dragging our feet to get this done."

The signing ceremony was a breakthrough moment for the nation's gay community, the military and for Obama himself. The president vowed during his 2008 campaign to repeal the law and faced pressure from liberals who complained he was not acting swiftly enough.