The top officers of the U.S. Army and Marine Corps told the Congress Friday it should not vote to allow homosexuals to serve openly in the military at this time, with combat troops entering their 10th year of war in Iraq and Afghanistan.

The day after U.S. Defense Secretary Robert Gates and the top U.S. military officer, Admiral Mike Mullen, told the Senate Armed Services Committee it should move quickly toward changing the law, the committee heard the service chiefs urge caution.

"My recommendation is that we should not implement repeal at this time," said General James Amos, the commandant of the Marine Corps. He was the strongest in his opposition to allowing homosexuals to serve without hiding their sexual preference, as they are required to do now.

"If the law is changed, successfully implementing repeal and assimilating openly homosexual marines into the tightly woven fabric of our combat units has strong potential for disruption at the small unit level, as it will no doubt divert leadership attention away from an almost singular focus on preparing units for combat," he said.

General Amos argued that with half of his force either in Afghanistan, just home or preparing to go, troops and commanders should not be distracted from the very serious business in front of them - staying alive in a combat zone and winning a war.

General Amos and the commanders of the Army, Navy, Air Force and Coast Guard were testifying about the just-released Pentagon survey of the troops and their families on the impact of changing the law known as "Don't Ask, Don't Tell" which President Barack Obama has promised to do.

The Chief of Staff of the Army, General George Casey, took a position similar to his Marine colleague's. "Implementation of the repeal of Don't Ask, Don't Tell in the near term will, one, add another level of stress to an already stretched force, two, be more difficult in our combat arms units, and three, be more difficult for the Army than the report suggests," he said.

Still, General Casey was more supportive in principle of a change in the law, but not now. He had this exchange with Senator John McCain.

Casey: "Eventually, I believe it should be repealed. The question for me, as I've said, is one of timing."

McCain: "And at this time?"

Casey: "I would not recommend going forward at this time, given everything the Army has on its plate."

The head of the Air Force, General Norton Schwartz, who has thousands of his troops deployed with Army units in Afghanistan, was also cautious. "I remain concerned with the study assessment that the risk of repeal (on) military effectiveness in Afghanistan is low. That assessment, in my view, is too optimistic," he said.

General Schwartz suggested postponing any change until 2012, saying next year will be too intense a period in the combat zone.

The head of the U.S. Navy, Admiral Gary Roughead was supportive of the change and did not indicate any concern about the timing. "Based on my professional judgment, and informed by the inputs from our Navy, I recommend repeal of 10 U.S. Code 654 (the Don't Ask, Don't Tell law)," he said.

The Coast Guard commandant (Admiral Robert Papp Jr.) also endorsed the effort to change the law.

The testimony by the military leaders was highly anticipated in the politically charged atmosphere of the "Don't Ask, Don't Tell" debate. Much like their testimony, the Pentagon study provides support for both sides, indicating that 70% of all service members believe the impact of changing the law will be negligible, but also saying that figure for troops in combat units is only about 40%.

Supporters of repealing the law believe their best chance is now, during the final session of the current Congress, before Republicans take control of the House of Representatives in January, based on last month's election results.