MONS, Belgium (Reuters) – The United States will send 20,000 troops to Europe next April and May in its biggest military exercises on European soil since the Cold War to underscore Washington's commitment to NATO, a senior allied commander said on Tuesday.

Days after a NATO summit in London at which U.S. President Donald Trump called low-spending European allies “delinquent”, U.S. Major General Barre Seguin said the exercises, centered on Germany, will be the largest of their kind in 25 years.

“This really demonstrates transatlantic unity and the U.S. commitment to NATO,” Seguin, who oversees allied operations from NATO's military headquarters in Belgium, told Reuters.

Eager to deter Russia from any repeat of its 2014 annexation of Crimea from Ukraine, the U.S. Army will test its ability to transport the soldiers across the Atlantic to Belgium and the Netherlands and then move quickly east through Germany into Poland and along NATO's eastern flank.

The soldiers will join U.S. personnel stationed across the continent, as well as militaries from 18 NATO allies, to mass around 37,000 troops, before returning to the United States, in an echo of the 'Return of Forces to Germany', or 'REFORGER' maneuvers, of the 1980s.

“We have not demonstrated this ability to rapidly reinforce, from a transatlantic perspective … for 25 years or so,” said Seguin, saying he recalled the REFORGER maneuvers as a boy in school in Germany.

NATO has already sent battalions to the Baltics and Poland to deter potential Russian incursions but now aims to be able to sustain any military operations. European governments are also spending more on making troops combat-ready.

Russia says it has no intention of attacking NATO and accuses the alliance of destabilizing Europe.

While French President Emmanuel Macron has questioned the U.S. commitment to NATO because of Trump's unrelenting criticism of allies, the U.S. president has also confounded Europeans by strengthening America's military presence in Europe.

Seventy years since its Cold War-era founding as an alliance focused on Moscow, Russia's efforts to undermine Western democracies through cyber attacks, disinformation campaigns and covert operations have given NATO a renewed sense of purpose.

The U.S. military has also put countering China and Russia at the center of national defense strategy, shifting priorities after focusing on the fight against Islamist militants.

“We're going into an era of strategic competition in peacetime,” Seguin said. “The alliance has reorientated.”