United States Vice President Dick Cheney has vowed that the administration would not allow an early withdrawal of US forces from Iraq, despite efforts by Congress to impose a deadline on US combat operations there. Late Saturday, Cheney defied a historic vote in the House of Representatives, which called for a pullout of US combat troops from Iraq by August 31, 2008 - regardless of whether Iraqi security forces are ready to take over from them. "A sudden withdrawal of our coalition would dissipate much of the effort that has gone into fighting the global war on terror, and result in chaos and mounting danger," the vice president declared. "And for the sake of our own security, we will not stand by and let it happen."