President George W. Bush's top military adviser said on Sunday setting an unconditional two-year timetable for getting U.S. troops out of Iraq in two years would be dangerous.

But Adm. Michael Mullen, chairman of the Joint Chiefs of Staff, said he would be able to recommend more troop reductions this fall if conditions there continued to improve.

Asked about a hypothetical two-year withdrawal timeline, Mullen told "Fox News Sunday, "I think the consequences could be very dangerous."

"I'm convinced (that) making reductions based on conditions on the ground are very important. We've been able to do that. We've reduced five brigades in the last several months and, again, if conditions continue to improve, I would be able to make recommendations to President Bush in the fall to continue those reductions."

The White House said on Friday that Bush, who has long opposed any set schedule for a withdrawal, had agreed with Iraq's prime minister to consider a "time horizon."