Iraq's vice president says a "quick" withdrawal of U.S. forces from his country would lead to chaos, and is not in the best interests of the Iraqis, the United States or other Western nations.

Tariq al-Hashemi spoke to reporters in Japan, hours after the Democratic-controlled U.S. House of Representatives approved a military spending bill that requires U.S. forces to be withdrawn from Iraq by August 2008.

The vice president said Iraq's armed forces are not yet ready to take over security functions from U.S. troops. He added that it will take at least 18 months to properly train Iraqi forces before U.S. troops can be systematically withdrawn.

President Bush has threatened to veto the House measure, saying the action only delays the delivery of vital resources for U.S. troops. .

Nancy Pelosi (file photo)

House Speaker Nancy Pelosi and other House Democratic leaders called the vote a giant step toward ending the administration's failed Iraq policies while forcing Iraqis to fight their own war.

The Senate may vote as early as next week on its own version of the war funding bill and a deadline for withdrawing troops.

The two versions would then need to be reconciled, with neither the House nor the Senate expected to have the votes needed to override the president's threatened veto.

Some information for this report was provided by AFP, AP and Reuters.