Britain could host American cruise missiles amid heightened tensions with Russia, Philip Hammond has indicated.
The Foreign Secretary said there were "worrying signs" about the increased activity of Russian forces and the UK would consider the pros and cons of taking US intermediate-range weapons.
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Mr Hammond said there was "no clear sign" of an imminent attack on Ukraine but Vladimir Putin is "keeping his options open".
But he warned against making "unnecessary provocations" against Russia, which has a "sense of being surrounded and under attack".
"He (Putin) has not ruled out a military option and as we go into the G7 meeting and then to the European Council later this month renewing sanctions, we have got to send very clear signals to the Russians that we will not tolerate any breach of their obligations under Minsk," he told BBC 1's Andrew Marr Show.
The Pentagon is looking at axing a Cold War-era treaty and deploying nuclear-capable missiles in Europe in response to Russia's breaches of international law, according to reports earlier this week.
The Americans are reported to be increasingly wary of an increased military presence by Russia, with Vladimir Putin’s regime moving to place missiles on Kaliningrad in the Baltic Sea.
Asked if he would back plans to re-introduce US missiles to Europe, Mr Hammond said: "I would need to see the detailed case for that. I haven't seen a detailed case for it.
"I think it is right to be concerned about the way the Russians are developing what they call asymmetric warfare doctrine."
Pressed on whether that would be a way to send a message to the Russian president, he replied: "It could be, but I think we have got a very delicate act to perform here.
"We have got to send a clear signal to Russia that we will not allow them to transgress our red lines.
"At the same time, we have to recognise that the Russians do have a sense of being surrounded and under attack and we don't want to make unnecessary provocations."