UNITED NATIONS - The UN Security Council moved swiftly to start what will likely be a months-long process to deploy the first significant UN peacekeeping force in conflict-wracked Darfur following the Sudanese government's long-awaited approval.

Council members immediately started the process of getting UN funding for the 3,000 troops, police and other personnel -- as well as six attack helicopters and other aircraft and equipment -- to beef up the beleaguered African Union force which has been unable to halt Darfur's four-year conflict.

The UN's most powerful body called on the Sudanese government late Monday to facilitate "the immediate deployment" of the so-called "heavy support package," which is the second phase of a UNplan to help the 7,000-strong African Union force. But it made clear the UN goal is deployment of the third and final phase -- a 20,000-strong "hybrid" UN-AU force.

"The heavy support package, as its name indicates, is not the robust force that Darfur needs," UN peacekeeping chief Jean-Marie Guehenno said. "It's a support package to lay the ground for a future robust force. It's a transition to a hybrid mission. That's how we see it."

After five months of stalling, Sudan gave a green light on Monday for the UN to send the 3,000 peacekeepers with their helicopter gunships, which Khartoum initially opposed.

Sudan's UN Ambassador Abdalmahmood Abdalhaleem informed Secretary-General Ban Ki-moon that the government hopes "that implementation of the heavy support package would proceed expeditiously."

The agreement was announced as Ban began two days of meetings on Darfur with AU chief executive Alpha Oumar Konare and the two envoys trying to promote a political settlement of the four-year conflict, the UN's Jan Eliasson and the AU's Salim Ahmed Salim. The secretary-general said he planned to discuss "the future course of action" at a wrap-up session Tuesday.

Ban called the agreement "a very positive sign," and Konare said he was "delighted" that issues over the "heavy support package" had finally been resolved.

The secretary-general said the UN will consult with the Sudanese government and expects Khartoum "to urgently provide the land and other facilities necessary for the deployment of the heavy support package, including permission to explore for water," UN spokeswoman Michele Montas said.

Ban urged all countries to contribute troop and police quickly for Darfur, but it likely will take months before the UN contingent is on the ground because the UN has no standing army and must rely on the goodwill of its 192 member states.

Konare stressed that the African Union needs international funding to keep its troops in Darfur.

"Let's be honest, without any sustainable financing, all this operation might not be as successful as expected," he said.

Britain's UN Ambassador Emyr Jones Parry, the current Security Council president, said he sent a letter to the secretary-general late Monday on behalf of the council asking Ban to seek General Assembly approval to fund the UN share of the heavy support package.

But Guehenno, the UN undersecretary-general for peacekeeping, said the AU will also need help from donors because it will be "several months" before the heavy support package can deploy.

He said it is also "critical" that two additional African Union battalions arrive in Darfur quickly to help provide "a minimum of security" for deployment of the 3,000 UN peacekeepers.

"It's kind of a chicken and egg situation," Guehenno said. "You need security to bring additional security, but the additional personnel will then contribute to security."

Sudanese President Omar al-Bashir has repeatedly rejected a UN force. But he has come under increasing pressure from the United States, the European Union, some Arab and African countries, and recently close ally China, which buys two-thirds of Sudan's oil exports and sells Khartoum weapons and military aircraft.

Though al-Bashir's government has a history of finding loopholes in agreements with the UN and others, the deal reached Monday appeared to be a significant step forward in bringing a more effective peacekeeping force to Darfur.

Nonetheless, U.S. diplomats and UN officials said they remain cautious until the UN peacekeepers are on the ground in the vast western province where more than 200,000 people have been killed and 2.5 million have been displaced since the conflict began in 2003.

"We'll see whether they've agreed when they actually start to deploy," acting U.S. ambassador Alejandro Wolff told reporters. "We all need to be vigilant -- that is understood and agreed by every person in (the) council. ... The test is going to be the implementation."

Wolff also indicated that further Sudanese conditions or delays could lead the council to consider "other measures," presumably additional sanctions.

The United Nations and Sudan agreed in November on the three-stage plan to strengthen the undermanned and under-equipped AU force in Darfur.

The first phase, a light support package including UNpolice advisers, civilian staff and additional resources and technical support, has already been sent to Darfur. Now that Khartoum has given its approval to the heavy support package, UN and AU officials will start focusing on deployment of the AU-UN force with 17,000 troops and 3,000 police officers.

Al-Bashir has said he would only allow a larger AU force, with technical and logistical support from the United Nations. He has maintained that deployment of UN troops would violate Sudan's sovereignty.

On Monday, after meeting with Malaysia's visiting prime minister, he called for Islamic nations' help in "working with Sudan to face the Western pressures on it to accept international forces."

At the same time, Sudanese Foreign Minister spokesman Ali al-Sadiq said Monday Sudan has also agreed to the larger deployment. But he said the UN had to send a team to Khartoum and a "tripartite committee" of UN, AU and Sudanese experts will decide on the details and timing of the entire force.

"This is a very significant step to solving the problems in Darfur," al-Sadiq said. "We hope it will ease the pressure."

Guehenno said there is already an agreement that the commander and deputy commander of a hybrid force will be Africans, along with the secretary-general's special representative. But he said "the command and control structures will be provided by the United Nations."

The UN-AU force will be looking for African troops, Guehenno said, but if the UN can't find enough "we will be looking elsewhere."