NORTH-WEST LONDON — Britain and nine European countries signed a statement of intent last week to create a multinational maritime force under the Joint Expeditionary Force to deter Russian threats from the open sea border to the north. The unit will act as a complement to NATO and will not include the United States.

The Joint Expeditionary Force includes the Netherlands, all five Nordic states and the three Baltic states, with the United Kingdom as its largest military member. Canada is considering joining. If required, the maritime force would be commanded from the UK's military headquarters in Northwood, north-west London.

"Russia remains the gravest threat to our security," First Sea Lord Gen Sir Gwyn Jenkins said. Jenkins also said that "Russian incursions into our waters has jumped by almost a third in the last two years."

Earlier this month, the UK said Russian spy submarines had been tracked engaging in what appeared to be covert surveillance of undersea infrastructure around Britain. Jenkins said the UK had an "open sea border with Russia to the north." Posing questions about the state of readiness, he said: "Were we prepared enough? Can we fight today, and if so, with what?"

Jenkins said the Middle East crisis had put the navy in the spotlight, and that uncrewed escort ships — large sea drones — would sail alongside UK warships in the next two years.

The UK has threatened to seize Russia-linked "shadow fleet" tankers exporting sanctions-hit oil but has not done so, while other European countries have successfully seized such vessels. Russia has committed frigates to escort vessels under sanctions through the Strait of Dover, despite a UK warning from Prime Minister Keir Starmer on 25 March. Since that date, 98 tankers subject to sanctions have passed through British waters.