Senator Sam Brownback of Kansas, who was joined by Congressman Frank Wolf of Virginia, urged U.N. Secretary General Annan to take immediate steps to end the genocide in Darfur.
"We cannot wait any longer for credible action in Darfur," he said. "The time is now for the Secretary General Kofi Annan to lead or leave."
Congressman Wolf says stopping the killing in Darfur would be a test of whether the United Nations can remain relevant.
"If in the year 2005 we [the Security Council] cannot deal with genocide, the raping of women, and the systematic burning of villages now occurring, then I believe it is fair to ask: what purpose is the United Nations serving in the 21st century," he said.
Congressman Wolf and Senator Brownback, both Republicans who visited Darfur last July, criticize a U.N. report for failing to recommend any action to stop the killing.
The report by a U.N. panel released Monday says the Sudanese government and its Arab Janjaweed militia allies committed crimes against humanity, but it stops short of labeling the violence genocide. The report refers the matter to the International Criminal Court.
Senator Brownback calls for expanding and accelerating the deployment of peacekeeping troops in Darfur, and imposing sanctions on the Sudanese government.
"The United Nations should vote to immediately levy hefty and serious economic and diplomatic sanctions against the government of Sudan, the government-sponsored janjeweed, and any businesses or companies complicit through their government connections," he said. "We must insist upon an arms embargo against the government of Sudan, travel restrictions against Sudanese government officials and a freeze on the assets of companies controlled by the ruling party that do business abroad."
Mr. Brownback also calls on Secretary General Annan to remove Sudan from the United Nations Commission on Human Rights.
At the United Nations, spokesman Fred Eckhard said Mr. Annan's authority is largely limited, with member states having the real power.
"The most the secretary-general can do under the charter is bring to the attention of the Security Council any threat to international peace and security," he said.
The United Nations says the two-year-old conflict has left some 70,000 people dead.