American officials said they were proceeding nonetheless.
While no final decision has been made on how many troops will be transferred from Africa and the Middle East as the Pentagon refocuses its priorities to confront “great powers” like Russia and China, America’s top military officer said the United States needed to shift its forces to better counter China in particular.
Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, acknowledged that the proposal was “causing some anxiety.” But he said that the United States needed to seriously re-examine its military footprint in Africa, and the Middle East and Latin America after that, given the heightened focus on China.
General Milley’s comments came ahead of a NATO military chiefs’ meeting in Brussels, where he also sought to lay out the United States’ rationale for killing Iran’s top military commander, Maj. Gen. Qassim Suleimani this month. The killing of General Suleimani, who was the head of Iran’s Islamic Revolutionary Guards Corps’ Quds Force, has raised questions from America’s military allies about whether commanders of sovereign countries are now fair game for drone strikes.
The Pentagon is also asking Europe to do more in the Middle East. After the killing of General Suleimani, Mr. Trump called for NATO to step up efforts to train Iraqi forces to fight the Islamic State in their country — a point that General Milley elaborated on at the NATO meeting on Tuesday.
One way European allies could help in Iraq, he said, was to provide ballistic missile defence systems at bases that house troops from the American-led coalition that has been fighting the Islamic State. Iran fired several ballistic missiles at two such bases in Iraq last week, though no one was killed.
In Africa, the Trump administration wants European allies, particularly the French, to pick up a bigger share of the battle against extremist Islamist organizations like the Islamic State, Al Qaeda in the Maghreb and Boko Haram.
The Pentagon’s discussions of a large-scale pullback from West Africa include abandoning a recently built $110 million drone base in Niger and ending assistance to French forces battling militants in Mali, Niger and Burkina Faso.
President Emmanuel Macron of France, in his own meeting with leaders of five West and Central African nations on Monday, pledged to send a further 220 French troops to the region, supplementing the 4,500 who are already there. Mr. Macron had called the meeting in an effort to persuade the African leaders to make clear publicly that they wanted the French forces to remain.
With the Pentagon expected to make its initial decision about Africa this month, the United States’ plans have already drawn criticism from lawmakers, allies and military officials, and could eventually affect most global missions. About 200,000 United States forces are stationed abroad, a similar number to when President Trump took office with a promise to conclude the nation’s “endless wars.”
Responding to General Milley’s comments on Monday, an aide to Mr. Macron told the news agency Agence France-Presse that American contributions to the fight against Islamic extremist groups in West Africa were “irreplaceable.”
General Milley said that no final decision had been made and that the Pentagon was reviewing American force posture all over the world. (United States military officials said that Africa was first because it begins with “A.”)
The Pentagon says that the overhaul of African deployments will be followed by one in Latin America and that drawdowns will occur in Iraq and Afghanistan, as it has outlined in recent months.
But the killing of General Suleimani, which has sharply exacerbated tensions between Washington and Tehran, could undermine the Pentagon’s plans. Since that killing, it has sent thousands of additional troops to the region to protect against possible strikes from Iran.