UNITED NATIONS (AP) — The U.S. pledged up to $60 million Monday to help a 5,000-soldier African force get going on fighting extremists in western Africa's vast Sahel region, but Washington remains cool to putting U.N. resources into the nearly $500 million-a-year effort as Sahel countries look to the world body for financing.

The promise of U.S. money announced separately by U.N. Ambassador Nikki Haley and Secretary of State Rex Tillerson comes after the region's dangers hit home for Americans with the deaths of four U.S. soldiers in Niger on Oct. 4. Niger is among the "Group of Five" countries launching the joint military force, along with Mali, Burkina Faso, Mauritania and Chad.

The nations have been grappling with a growing menace from extremists, including the Islamic State group, Boko Haram and groups linked to al-Qaida's North Africa branch.

"These threats are real," Burkina Faso's foreign minister, Alpha Barry, told the Security Council on Monday, days after members returned from a visit to the region.

About 5 million people in the region have been displaced, according to U.N. Secretary-General Antonio Guterres. The U.N. peacekeeping mission in Mali has become the world's most dangerous, with its convoys routinely attacked by Islamic militants. Three peacekeepers were killed in a convoy attack just last week.

In Burkina Faso, over 2,000 children in one province haven't been able to go to school this fall because of terrorist attacks in a country where teachers have been killed, Barry said. Schools and town halls have been set afire, mayors and town councilors abducted. Some 80 terror attacks have killed 133 people, some of them foreigners, in his country in the last 18 months.

"To eradicate the terrorist threat in Burkina Faso and each one of our countries will mean protecting all the other countries, including your countries," Barry told the council.

The Group of Five agreed in February to assemble a force to combat extremist groups, organized crime and human trafficking. A headquarters is now operating in Sevare, Mali, and the first cross-border operations are expected to start soon, Malian Foreign Minister Abdoulaye Diop told the council.

But facilities, equipment, training and other needs remain to be met in a region with limited resources, Guterres said in a recent report. It outlined various possibilities for U.N. support, either through the Mali peacekeeping mission or separately. He urged the council Monday to "be ambitious."

"We owe it to the populations of the Sahel," Guterres said.

Diop said at a news conference that the Group of Five countries hope for "predictable, enduring" financial support from the world body. Before the U.S. pledge, about a quarter of the force's estimated 423 million-euro ($492 million) first-year budget had been raised. It included 50 million euros ($58 million) from the European Union, which is organizing a fundraising conference in Brussels in December.

French Foreign Minister Jean-Yves Le Drian urged Security Council members to provide U.N. aid. It would give the Sahel force a sustainable source of funding and "an important signal of international support," he said.

France has about 5,000 of its own soldiers fighting extremists in the five countries and proposed Security Council authorization in June for the Group of Five effort. The proposal was watered down to only welcome the deployment, at the insistence of the U.S., which wanted to foreclose the possibility of U.N. funding.

Haley told the council Monday that the U.S. still has "serious and well-known reservations about using U.N. resources to support non-U.N. activities" and is reluctant to add to the Mali peacekeeping mission's responsibilities. But the U.S. pledge of $60 million, Tillerson said in a statement, "will play a key role" in the Group of Five's fight against extremists.

Diop said the U.S. support was "very important," and the five nations hope for more support as U.N. discussions continue.

"We are also ready to play our part," he said. "But what we are tackling is ... a global threat that we shouldn't be left alone to deal with."