(CNN) Defense Secretary James Mattis said Saturday that Russia attempted to interfere in the US midterm elections last month.

"(Putin) tried again to muck around in our elections this last month, and we are seeing a continued effort along those lines," Mattis said, speaking at the Reagan National Defense Forum at the Ronald Reagan Presidential Library in Simi Valley, California.

Mattis said the relationship between the United States and Russia has "no doubt" worsened amid Russia's continued efforts to intervene in the US electoral process.

Mattis said he didn't know if the threat from Russia had increased, but he said Russian President Vladimir Putin has "continued efforts to try to subvert democratic processes that must be defended,"

"We'll do whatever is necessary to defend them," Mattis later added.

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