Bush adviser says Iraq timeline 'very dangerous'

(Adds comments from Condoleezza Rice on CNN)

WASHINGTON, July 20 (Reuters) - 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."

Mullen said such a goal, which would be part of a security agreement being negotiated between the two countries, sends a signal that "eventually we do want to bring our troops home."

He said his mission from Bush was to advise on troop withdrawals "exclusively based on conditions on the ground."

"I'd worry about any kind of rapid movement out and creating instability where we have stability," he said.

Secretary of State Condoleezza Rice told CNN in an interview that with violence in Iraq declining and the political system there functioning better, "we would be foolish and they would be foolish to put at risk those gains by too rapid a decline in the American forces there.

"But we can look at the situation, we can have an aspirational time horizon, we can look at the changing roles and responsibilities of Iraqis and Americans. Those are all perfectly logical things to do," Rice told CNN's "Late Edition."

The last of five extra combat brigades that Bush sent to Iraq in 2007 will finish withdrawing next week, leaving 140,000 U.S. troops there. Bush had ordered the "surge" of forces to stop Iraq's slide into sectarian civil war.

The White House avoided the words "timetable" or "timeline" in announcing the agreement with Iraqi Prime Minister Nuri al-Maliki.

Iraqi policy has been a central issue in the battle for the U.S. presidency between Democrat Barack Obama and Republican John McCain.

Mullen's comments came as Obama, who has vowed to withdraw troops from Iraq within 16 months of taking office, prepared to visit Iraq. The Illinois senator has said his goal for withdrawal was open to tactical adjustments."

McCain supports the Bush policy of determining troop withdrawals based on the situation on the ground.

(Reporting by Doina Chiacu and Paul Eckert; Editing by Doina Chiacu)