NATO will deploy four international battalions to Poland and the three Baltic states as part of the wider pushback against Russia's intervention in Ukraine, alliance head Jens Stoltenberg said Monday.

"We will agree to deploy by rotation four robust multi-national battalions in the Baltic states and Poland," Stoltenberg told a news conference ahead of a meeting of NATO defence ministers in Brussels on Tuesday.

"This will send a clear signal that NATO stands ready to defend any ally," he said, referring to a whole series of measures the US-led alliance has taken since the Ukraine crisis to counter a more assertive Russia.

NATO leaders are due to sign off on the programme at a July 8-9 summit in Poland, which has pushed for a much harder line, including having permanent bases in the east to counter Russia.

Stoltenberg did not say how many troops would be deployed in the four battalions but officials previously have said they will number 2,500-3,000, acting as a tripwire to deter Russia and reassure nervous alliance members once ruled from Moscow.

The NATO chief stressed that the deployment -- to be made on a rotational basis, not permanent so as not to infringe existing treaties with Russia -- was part of a much wider response to the Ukraine crisis.

This includes tripling the NATO Response Force to 40,000 men ready to move at short notice, creating a Spearhead force of about 5,000 on a just few days standby.

It also includes pre-positioning equipment and headquarters units so these troops can hit the ground running in any fresh crisis.

Topping off the revamp is a commitment by NATO's 28 member states to reverse years of spending cuts and devote two percent of total national economic output to defence within a decade.

Stoltenberg said progress was being made in this crucial area, with the allies spending 0.6 percent more on defence last year and an increase of 1.5 percent expected in 2016.

He repeated that NATO's response to the Ukraine crisis was purely defensive and that it did not seek any "confrontation" with Russia.