U.S. President George W. Bush threatened on Wednesday to beef up economic sanctions and impose new punishments if Sudan fails to take concrete action to meet its obligations over Darfur crisis.

Sudan must follow through on the deployment of UN support forces and take every necessary step to facilitate the deployment of the full UN-African Union peacekeeping force, Bush said in remarks at the Holocaust Museum in Washington..

"The time for promises is over, (Sudanese) President Bashir must act," Bush said. "If President Bashir does not meet his obligations, the United States will act."

Sudan's envoy to the United Nations announced Monday that the Sudanese government has approved a UN plan to send attack helicopters to support the African Union (AU) force in war-torn Darfur.

The Bush administration planned to impose new, stricter sanctions on the Sudanese government over its handling of the Darfur crisis. The sanctions would include sanctions on 29 Sudanese companies, in addition to existing sanctions on 130 other Sudanese firms.

However, the United States decided to delay unilateral new sanctions against Sudan over the Darfur crisis to give the United Nations more time to negotiate with Khartoum, said Andrew Natsios, the U.S. special envoy to Sudan, last week.

The United Nations, the African Union and the Sudanese government agreed in November 2006 on the three-phase support plan which was also known as the Annan plan as it was put forward by then UN Secretary General Kofi Annan.

With the first phase of the plan, a light support package already underway, the three parties reached an agreement in principle in Addis Ababa on April 9 to inaugurate the second phase of a UN support plan for the AU mission in Darfur, known as "the heavy support phase."

But the Sudanese government's opposition for the deployment of attack helicopters in Darfur had blocked the scheduled implementation of the second phase.

In war-torn Darfur, at least 200,000 people have reportedly been killed since 2003 in ethnic and political conflict triggered by a rebellion.