The head of the US army in Europe said on Tuesday that a British exit from the European Union could trigger the unravelling of the bloc and thus weaken the NATO military alliance in relation to Russia.
"Anything that undermines the effectiveness of the alliance has an impact on us, and so if the EU begins to become unravelled there can't help but be a knock-on effect for the alliance also," Lieutenant General Ben Hodges said.
Opinion polls show that British voters are divided with a large number of people still undecided about Brexit.
Hodges, former commander of NATO’s Allied Land Command from 2012 to 2014, said that the vote was a matter for the British people but he was concerned about the impact on the NATO alliance.
"What goes on here is of strategic interest to us," Hodges said adding that NATO and the EU needed to show solidarity in what he described as Russian aggression.
Cameron criticised supporters of Brexit on Thursday saying that for those who support leaving, lost jobs and a dented economy might be collateral damage, or a price worth paying.
Hodges also said that Russia had “weaponised” the refugee crisis by forcing tens of thousands of people to flee to Europe.
United States President, Barack Obama, is set to travel to London in April and urge British voters to support membership of the European Union.
Russia rebuked Britain for saying Russian President Vladimir Putin dreams of weakening the West with a British exit from the EU bloc.
Cameron announced a referendum will be held on June 23 where British people will decide whether the country's future will be in or out of the EU.