On a visit to the Baltics, Pence denounced Russia as an "unpredictable neighbor" that sought to "redraw international borders by force."
Pence's intervention, on a visit to the Estonian capital of Tallinn, came a day after President Vladimir Putin announced he would gut US missions in the country. That decision came after US Congress passed a bill last week to slap fresh sanctions on Russia
over its 2016 US election meddling.
Any prospect of a reset of US-Russian relations, previously advocated by both Putin and US President Donald Trump, now appears slim.
"At this very moment, Russia continues to seek to redraw international borders by force, undermine democracy in sovereign nations, and divide the free nations of Europe, one against another," Pence said at a press conference, alluding to the Russian annexation of Crimea.
"Under President Donald Trump, the United States of America rejects any attempt to use force, threats, intimidation, or malign influence in the Baltic states or against any of our treaty allies."
Speaking alongside presidents of Estonia, Lithuania and Latvia, Pence sought to assure the Baltic leaders that the US would not be intimidated by Putin's announcement Sunday that US missions would be stripped of 755 staff members and two properties. There are around 1,200 staff members working at these missions, though it is not clear how many are US citizens.
"To be clear, we hope for better days, for better relations with Russia, but recent diplomatic action taken by Moscow will not deter the commitment of the United States of America to our security, the security of our allies, and the security of freedom loving nations around the world," he said.
Retaliation for Obama sanctions
Putin is seeking to reduce the number of staff members at US missions in Russia to 455, a figure equal to the number of Russian diplomats now in the United States, the Russian Foreign Ministry said earlier, giving a deadline of September 1 for the cuts.
Putin's decision to cut staff members was also a delayed retaliation to sanctions imposed at the end of Barack Obama's presidency in 2016, when the US expelled 35 Russian diplomats from the country and seized two compounds used by Russian missions. Those actions were in response to Russia's election meddling, as well as its continued military aggression in Ukraine.
When asked if there was a way out of the political impasse, Kremlin spokesman Dmitry Peskov said there needed to be the political will to restore relations and called for the sanctions against Russia to end.
But Peskov also said that Putin and Moscow were interested in cooperating with the US "where it fits our interests."