A Pentagon survey has shown US Marines are "predominantly" opposed to lifting a ban on gays serving openly in the military, a top general said Tuesday.

General James Amos, nominated to lead the US Marine Corps, revealed the survey results to lawmakers as the US Senate weighed whether to end the ban.

As part of the administration's plans to end the ban, the Pentagon has carried out an elaborate survey of marines and other service members at military bases and online, but the results have yet to be released.

"I've heard at the Marine bases and the Marine input for the online survey has been predominantly negative," Amos told the Senate Armed Services Committee.

But Amos added he had heard about the results second-hand and had not seen the survey responses.

The Senate on Tuesday faced a pivotal vote on a bill that includes a repeal of the 1993 law, which requires gay service members to hide their sexual orientation or face dismissal.

The outgoing Marine commandant, General James Conway, has been an outspoken opponent of ending the ban and members of the Marine Corps are widely seen as mostly opposed to changing the rule.

In written testimony to the committee, Amos also said he opposed changing the law, which he described as a "reasonable" compromise.

He said he was worried that repealing the ban could be disruptive at a time when nearly 20,000 marines are engaged in major combat in Afghanistan.

"I?m concerned that a change now will serve as a distraction to Marines who are tightly focused at this point on combat operations in Afghanistan," Amos wrote.

Amos was questioned about the survey results by Republican Senator John McCain, who has vowed to block a bill that would end the ban.

Supporters of lifting the ban say the current policy harms the country's national security by forcing out qualified, committed troops.

Amos, however, said he was confident that if the law is repealed, the Marines would enforce the new rule without hesitation.

"We obey orders," he said.