The chairman of the US Joint Chiefs of Staff will meet with his Russian counterpart Thursday, the Pentagon said.

The meeting in the former Soviet republic of Azerbaijan comes amid reports that aides to Donald Trump had repeated contact with Russian intelligence during the US presidential campaign.

But the United States insisted Wednesday that the meeting between General Joe Dunford and the Russian military chief, General Valery Gerasimov, was not political in nature and had been planned for months.

The two men will talk about US-Russian military ties and "the importance of consistent and clear military-to-military communication to prevent miscalculation and potential crises," the Pentagon said.

The meeting comes with the White House in crisis mode after the resignation Monday of national security adviser Michael Flynn.

His resignation followed revelations that he did not give the White House a complete account of conversations he had with the Russian ambassador about US sanctions against Moscow before Trump took office in January.

Flynn, like Trump, has supported warmer ties with Russia.

Dunford said last year he was eager to meet with Gerasimov.

NATO allies must pay more or US will 'moderate its commitment': Mattis
Brussels (AFP) Feb 15, 2017 - US Defence Secretary James Mattis warned NATO allies Wednesday that Washington would "moderate its commitment" to the alliance unless they boost their spending.

"No longer can the American taxpayer carry a disproportionate share of the defence of Western values," Mattis said in prepared remarks given to his counterparts at NATO headquarters in Brussels.

"If your nations do not want to see America moderate its commitment to this alliance, each of your capitals need to show support for our common defence."

Washington has long insisted that NATO members should spend two percent of their GDP on defence, a goal that few meet despite agreeing on it at a summit in Wales in 2014.

Consecutive US defence chiefs have hammered NATO on the topic for years, but Mattis's call for cash -- and his blunt language -- carries extra weight as it comes after Trump while campaigning said US help for NATO allies might be contingent on how much they have paid.

"Americans cannot care more for your children's future security than you do," he said.

Mattis called for "milestone dates" this year that would track NATO member contributions.

Currently, only the United States, Britain, Estonia, Greece and Poland have hit or surpassed the two percent figure.

"We must ensure we are not in the same spot at the end of the year that we are in today," Mattis said.