Donald Trump's new administration understands the need to deal with Russia in a "very guarded way", Foreign Secretary Boris Johnson has said.
Following his first meeting with US secretary of state Rex Tillerson during the G20 summit in Germany, Mr Johnson, referring to Russia, said "you've got to beware of what they are up to".
Neither side wants to see a return to the days of the Cold War, he said.
But Moscow's current behaviour cannot be allowed to continue, he added.
Mr Johnson's comments come amid intense scrutiny in the US of the administration's attitude to Russia following the resignation of national security adviser Michael Flynn over his contacts with the Russian ambassador to the US before Mr Trump's inauguration last month.
Mr Johnson told the BBC: "I think Rex Tillerson is absolutely clear in his view, which is the same as mine. You have got to engage with Russia, but you have got to engage in a very guarded way. You have got to beware of what they are up to.
"There is no question that, when you look at Russian activity on the cyber front, when you look at what they are doing in the western Balkans, when you look at what has been happening in the Ukraine, you've got to be very, very cautious.
"I think it is entirely right to have a dual track approach.
"We don't want to get into a new Cold War. That's something London and Washington are completely at one on. But nor do we want Russian behaviour to continue as it is - and Rex Tillerson has been very clear about that."