Russia said it test fired a new intercontinental ballistic missile, a move President Vladimir Putin said would give the U.S. and its allies something to think about.

It almost certainly ups the ante almost two months since Russia invaded Ukraine and it comes at a delicate moment in the conflict as its forces step up their offensive in the eastern Donbas region.

The Russian leader was shown on state television watching a video of the missile launch and remarked that “this unique weapon will strengthen the military potential of our armed forces, will reliably guarantee Russia’s security against outside threats and force those, who in the heat of frenzied aggressive rhetoric try to threaten our country, to think again.”

The Sarmat intercontinental ballistic missile was fired from the Plesetsk Cosmodrome in the northern Arkhangelsk region, the Defence Ministry said. The ministry previously showed videos of the latest generation missile in 2018. U.S. Defence Department spokesman John Kirby told reporters that normal notification procedures were followed ahead of the test.

Putin has signalled the possibility of escalation, ordering Russia’s strategic nuclear forces on high alert just days after his troops moved into Ukraine. He also warned that any intervention by other countries in the conflict would trigger “consequences you have never seen.”

U.S. and European arms deliveries have helped Ukraine blunt the Russian attack, which is refocused on the east after failed efforts to capture the capital Kyiv. At the same time NATO has ruled out a no-fly zone over Ukraine, given it would put the alliance’s planes in direct confrontation with Russian aircraft. And it has said it won’t send troops in to join the fight.

Foreign Minister Sergei Lavrov didn’t give a direct answer to repeated questions about whether Russia might use atomic weapons in Ukraine in an interview released Tuesday, though he said Moscow was firmly against nuclear conflict.

The top Russian diplomat’s comments came after a top Putin ally threatened to deploy nuclear weapons in and around the Baltic Sea if Finland and Sweden join the North Atlantic Treaty Organization.

“In this case there can be no talk of non-nuclear status for the Baltic,” Dmitry Medvedev, deputy chief of the Russian Security Council and former president, said last week, suggesting Russia may deploy Iskander missiles, hypersonic weapons and nuclear-armed ships in the region.