NATO's new supreme commander US General Curtis Scaparrotti said on Wednesday that he would "strengthen" the alliance's stance in eastern Europe against a resurgent Russia.

At a handover ceremony from his predecessor Philip Breedlove, the former commander of US forces in Korea also said NATO should consider whether to provide Ukraine with weaponry as it battles pro-Russian rebels.

Scaparrotti's comments came as Russia's defence minister announced that Moscow will set up three new divisions in the west and south by the end of the year to counter NATO forces close to its border.

The US general said Breedlove's moves to boost NATO's presence on its eastern flank following Russia's annexation of Crimea in 2014 and increasingly assertive stance in the region were "correct".

"I plan to continue and strengthen his plans as we work together and move towards the Warsaw summit" of the leaders of the 28 NATO nations in July, Scaparrotti told a press conference in Belgium with NATO chief Jens Stoltenberg.

He said one of NATO's biggest challenges was "a resurgent Russia striving to project itself as a world power".

"From everything I have seen, Russia has been very active in eastern Ukraine. I don't see any indication that that's going to change in the short term and I don't expect it will," the 60-year-old Scaparrotti said.

"Having to do with weaponry, I do believe we should support the Ukrainians with what they need to successfully defend their territory and their sovereignty," he said, adding "I need to assess what weapons are best, what capabilities they can use."

Stoltenberg insisted that the alliance's increased presence in east was a response to Moscow's own aggressive behaviour in eastern Ukraine, where it is accused of fuelling a separatist insurgency against a pro-Western government in Kiev.

"We didn't have any troops in Baltic countries... before the illegal annexation of Crimea and Russia's destabilising activities in eastern Ukraine," he said.

"So what we do is defensive, it's proportionate, and it's fully in line with our international obligations."