Tillerson made the remarks on Sunday after he held a meeting with Russian Foreign Minister Sergei Lavrov in Manila, the Philippines, where they attended the Association of Southeast Asian Nations (ASEAN) summit.
The top US diplomat said he had warned Lavrov that the United States would respond to Moscow’s decision of expelling hundreds of American diplomats from Russia.
"Russian meddling in the elections was certainly a serious incident. We talked about that in the discussion that we had with Mr. Lavrov yesterday," Tillerson told reporters.
"And trying to help him understand just how serious this incident had been and how seriously it had damaged the relationship between the US and the American people and the Russian people, that this had created serious mistrust and that we simply have to find some way to deal with that,” he added.