BRUSSELS - European Union defence ministers paved the way on Tuesday for Britain to join an EU project aimed at facilitating the swift movement of troops and military equipment across Europe, as war rages in Ukraine for a ninth month.

Britain, which formally left the EU in 2020, four years after voting in a referendum to leave the bloc, has long been sceptical about moves towards greater European military integration, fearing this could undermine NATO.

But non-European NATO allies the United States and Canada have also signed up to the EU's "Military Mobility" project, part of its enhanced defence cooperation (PESCO). It aims to simplify and standardise procedures for military personnel and equipment as they cross borders by road, rail, sea or air.

Military experts have long complained that red tape is hampering the swift movement of personnel and equipment that would be crucial if NATO allies had to send reinforcements to eastern Europe in the case of a conflict.

"Russia's war against Ukraine has further demonstrated that being able to move troops and military equipment swiftly across Europe and beyond is essential for our security," EU foreign policy chief Josep Borrell said in a statement.

"After the U.S., Canada and Norway joined last year, the UK's participation is yet another proof of the importance of this project," he said.

"Ensuring fast movement and secure transport of armed forces is crucial to improve the EU and NATO's ability to respond to crises, in particular now as we provide urgent military support to Ukraine."

Britain is one of the most vocal critics of Russia's invasion of Ukraine. It has so far committed 3.8 billion pounds ($4.5 billion) in military and economic aid to Ukraine since the war began in February.

($1 = 0.8404 pounds) ($1 = 0.9611 euros)

(Reporting by Sabine Siebold; Editing by Gareth Jones)