U.S. President Barack Obama plans to withdraw most of U.S. troops out of Iraq in less than 19 months, pending a formal announcement later this week, officials said Tuesday.

Except a residual force between 30,000 to 50,000 to be left till December 2011, most of the 142,000 U.S. troops will be out of Iraq by August 2010, 19 months after Obama's swearing-in on Jan. 20, U.S. TV networks and wire services quoted administration officials as saying.

Obama is meeting with Secretary of Defense Robert Gates at the White House Tuesday afternoon and he is expected to make a formal announcement later this week, probably on Wednesday, they said.

The new withdrawal timetable will be three months later than Obama's original pledge to pull out most troops in 16 months after his inauguration.

Some 4,250 U.S. troops died and 650 billion U.S. dollars have been spent since the United States invaded Iraq in March 2003.

Editor: Yan