(CNN) - The U.S. government intends to have all its troops out of Iraq by the end of 2011, and it's up to the Iraqis to make that timetable work, Vice President Joe Biden said.
In an interview with ABC News' "This Week" during his trip to Iraq that ended Sunday, Biden said a collapse by Iraq into civil war once U.S. troops depart would be "a tragic outcome."
President Barack Obama remains committed to withdrawing combat troops by the end of August 2010 and all U.S. forces out by the end of 2011, he said.
"That is our intention," Biden said, noting that Iraqi elections scheduled for early 2010 would offer the nation an opportunity for a major step forward.
"It is our expectation that election will come out peacefully," he said.
On another issue, Biden refused to speculate on what the United States would do if Israel decided to attack Iran's nuclear facilities.
Israeli Prime Minister Benjamin Netanyahu has indicated such a strike could happen if Israel believes international efforts to curtail Iranian nuclear weapons production are failing.
Iran insists its nuclear program is intended solely for peaceful purposes.
Biden said Israel has the right as a sovereign nation to act in its own interests.
"We cannot dictate to another sovereign nation what they can and cannot do," he said.
The United States will continue working with allies to engage Iran in talks on halting its nuclear program, Biden said.
Participants in the so-called P5-plus-one talks have invited Iran to take part, he said, and it was up to Iran on whether to join in or remain isolated from the global community.
"There is no pressure from any nation that's going to alter our behavior with how to proceed what we believe is in the national interest of the United States, which we also believe is in the best interest of Israel," Biden said of the proposed talks.
The P5-plus-one includes the five permanent members of the U.N. Security Council - Britain, China, France, Russia and the United States - along with Germany.