BRUSSELS — Russia canceled a request to refuel a flotilla of its Syria-bound warships at a Spanish port Wednesday, according to Russian state-run media and other news reports. The move came amid mounting criticism leveled at Madrid from NATO’s secretary general and Britain’s defense minister.

The Russian battle group, containing cruisers, submarine-hunting warships and Russia’s lone aircraft carrier — the Admiral Kuznetsov — was set to refuel in Ceuta, a port in North Africa near the Strait of Gibraltar, before heading to the Mediterranean Sea. While Spain has allowed Russian ships to use its refueling facilities in the past, the small armada’s likely mission — bolstering Russia’s strikes in Syria — has drawn widespread condemnation, forcing Spain into an uncomfortable position with its allies.

“The Russian Embassy in Madrid has just informed us that it is withdrawing the request for permission for stopovers for these ships and these stopovers have therefore been canceled,” the Spanish Foreign Ministry said. The ministry has said earlier Wednesday that it was reviewing the Russian refueling request, the Reuters news agency reported.

A spokesman for the Russian Embassy in Madrid confirmed the cancellation to the Associated Press but gave no further details.

Before Russia rescinded its decision to refuel in Ceuta, British Defense Secretary Michael Fallon told reporters in Brussels that Britain “would be extremely concerned if a NATO member should consider assisting a Russian carrier group that might end up bombing Syria.”

“On the contrary, NATO should be standing together,” he added.

In recent weeks, the Kuznetsov, along with its escort ships, steamed through the North Sea and into the English Channel, drawing a wary eye from European countries that increasingly see Russia as a threat to their security.

The eight-ship battle group, reported to be accompanied by submerged escort submarines, will probably be used to increase Russian airstrikes in Syria, as Russian and Syrian government forces attempt to break resistance to their months-long siege of the city of Aleppo. The Kuznetsov, an aging Soviet-era aircraft-carrying missile cruiser, is set to provide a contingent of strike fighters that will join the already sizable Russian air force presence stationed in northeastern Syria.

“We are concerned about the possibility that the Kuznetsov carrier group can be used as a platform for more attacks against Aleppo and Syria, and thereby exacerbating the humanitarian catastrophe we already see in Aleppo and Syria,” NATO Secretary General Jens Stoltenberg said Wednesday before a defense ministerial meeting at NATO headquarters.

As Russia flexes its military capabilities both in Europe’s waterways and in the Middle East, NATO countries provided more details this week of their efforts to shore up a force designed to deter Russia. On Wednesday, U.S. Defense Secretary Ashton B. Carter outlined the type of units — including artillery and antitank weapons — that the United States is sending to reinforce NATO’s eastern flank. The move, announced in February under what the Pentagon calls the European Reassurance Initiative, includes sending a Stryker brigade into the Baltic states and Poland until they are replaced by four NATO battalions in April.

“It’s a major sign of the U.S. commitment to strengthening deterrence here,” Carter said.

Fallon also announced that Britain would be sending Typhoon fighters to Romania to patrol the region atop earlier commitments to send tanks, drones and 800 ground troops to Estonia in the coming months. The British forces will be supported by French and Danish troops. The British troop contingent is one of NATO’s four, 1,000-strong battalions that are to be led by the United States, Britain, Germany and Canada, and deployed throughout the Baltic states and Poland.

On Wednesday, Germany said it would send about 400 troops to Lithuania, supported by forces from Netherlands, Norway, Belgium, Croatia and Luxembourg. Canada is also sending about 400 troops, although they are headed to Latvia along with more than 100 Italian troops. The four battalions are in addition to a 40,000-strong response force designed to counter cross-border incursions of the kind undertaken by Russia in Crimea in 2014.

Stoltenberg said the alliance’s response is “proportioned” to Russia’s military buildup and its activities along its borders.

“This month alone, Russia has deployed nuclear-capable Iskander missiles to Kaliningrad and suspended a weapons-grade plutonium agreement with the United States,” Stoltenberg said.

The Iskander missiles are one more part of a growing arsenal stationed at Russia’s naval base in Kaliningrad, which includes advanced surface-to-air missiles that could target aircraft flying well into nearby Lithuania and Poland.

“These moves do not lower tensions or restore predictability to our relations,” he added.

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