Story highlights Mattis claims Russia has interfered in a number of elections

"Russia's aggressive actions have violated international law," Mattis says

(CNN) US Defense Secretary James Mattis said Thursday that the US is"not in a position right now" to collaborate with Russia on military matters.

Speaking at a NATO conference in Brussels, Mattis accused Russia of violating international law, labeling its actions as "aggressive" and "destabilizing."

Mattis, who spoke of the need to negotiate with Russia "from a position of strength" on Wednesday, was cool on any prospect of working with Moscow.

"We are not in a position right now to collaborate on the military level, but our political leaders will engage and try to find common ground," he said Thursday.

"Russia's aggressive actions have violated international law and are destabilizing."

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