Russia will move its tactical nuclear weapons close to the western borders of Belarus, the Russian envoy to Minsk said on Sunday, placing them at NATO’s threshold in a move likely to further escalate Moscow’s standoff with the West.

In one of Russia’s most pronounced nuclear signals since the beginning of its invasion of Ukraine 13 months ago, President Vladimir Putin said on March 26 that Russia will station tactical nuclear weapons in Belarus.

The two Slav neighbours are formally part of a “union state” and have been in talks for years to integrate further, a process that has accelerated after Minsk allowed Moscow to use Belarusian territory to send troops into Ukraine last year.

The weapons “will be moved to the western border of our union state and will increase the possibilities to ensure security,” Russian ambassador to Belarus, Boris Gryzlov, told Belarusian state television.

“This will be done despite the noise in Europe and the United States.”

Gryzlov did not specify where the weapons will be stationed, but confirmed that a storage facility will be completed, as ordered by Putin, by July 1 and then moved to the west of Belarus.

Belarus borders to the north with Lithuania and Latvia and to west with Poland, all part of NATO’s Eastern flank that has been bolstered with additional troops and military equipment following Russia’s invasion of Ukraine.

The US and Kyiv’s other allies have said they were concerned about the possibility that Russia would send tactical nuclear weapons to Belarus, with President Joe Biden saying it was “worrisome.”

President Alexander Lukashenko said on Friday that Belarus would also allow Russia to put intercontinental nuclear missiles there too if necessary.