( dpa ) - The United States is frustrated by the slow deployment of a UN peacekeeping force to Sudan's troubled Darfur region, the White House said Wednesday. "We remain very frustrated and we would like the rest of the world and the United Nations to fully back this effort and to put more pressure on the Sudanese," White House spokeswoman Dana Perino said. The comments follow a UN report on Tuesday that said only 40 per cent of the authorized UN force of 20,000 has reached Darfur and it will take until next year to have the complete force on the ground. "It's too long. Should have happened by now," US State Department spokesman Sean McCormack said. The United Nations will join up with an African Union force of 10,000 peacekeepers that have largely been ineffective at halting the violence. More than 300,000 lives have been lost in the conflict that began in early 2003.