NATO diplomats say the bloc remains uncertain of President Putin’s intentions this time around as Russia has thousands of troops along Ukraine’s border.

NATO members could impose
NATO members could impose "economic sanctions and political reactions" against Moscow, NATO Secretary General Jens Stoltenberg says. (AP)

NATO has warned Moscow it would pay a high price if it launches an invasion of Ukraine, as Russian President Vladimir Putin cautioned the West not to cross the Kremlin's "red lines".

"Any future Russian aggression against Ukraine would come at a high price and have serious political and economic consequences for Russia," NATO Secretary General Jens Stoltenberg said in a meeting on Tuesday.

Top diplomats from the US-led alliance met in Latvia's capital Riga looking to deter a Russian incursion as fears have grown after accusations Moscow has massed tens of thousands of troops and heavy weapons on its neighbour's borders.

"We need to be prepared for the worst and we need to convey a message to Russia that they should not conduct a military incursion into Ukraine," Stoltenberg said. 

Earlier US Secretary of State Antony Blinken threatened "serious consequences" if Russia moves into Ukraine. 

Moscow, which seized Crimea from Ukraine in 2014 and backs separatists fighting Kiev, has strongly denied it is plotting an attack and blames NATO for fuelling tensions.

READ MORE: EU, NATO vow action against threats posed by Belarus, Russia

Moscow equally concerned

Russian President Vladimir Putin has sternly warned NATO against deploying its troops and weapons to Ukraine, saying it would trigger a strong response.

Commenting on Western concerns about Russia's alleged intention to invade Ukraine, he said that Moscow is equally worried about NATO drills near its borders.

He added that Russia has been forced to counter the growing threats by developing new hypersonic weapons.

“What should we do?” Putin said. “We would need to develop something similar to target those who threaten us. And we can do that even now.”

The new build-up follows a similar surge in the spring, when Russia gathered around 100,000 troops on Ukraine's borders but later announced a drawdown.

NATO diplomats say the bloc remains uncertain of Putin's intentions this time round, but ministers were discussing contingency plans should Russia invade. 

Officials were weighing additional support for Ukraine's military and whether to strengthen NATO forces arrayed along its eastern wing. 

But they point out that NATO-aspirant Ukraine — which will have its foreign minister arriving for day two of the meeting on Wednesday — is not covered by the alliance's collective defence pact. 

Kiev has called for swift action to "deter" its Soviet-era master Moscow from invasion, saying that a Russian military operation could be launched "in the blink of an eye".

READ MORE: Biden plans to speak to Putin and Zelenskyy amid tensions

Source: TRTWorld and agencies