Washington "stands with the people of Ukraine and most especially since 2014, we have stood strongly for the territorial integrity of Ukraine," Pence said after meeting Ukrainian President Volodymyr Zelenskiy in Warsaw on September 1.
"And I can assure you that we will continue to stand with the people of Ukraine on your security, on territorial integrity, including Ukraine's rightful claim to Crimea," Pence said.
The United States is an important ally for Kyiv, having imposed sanctions on Russia for annexing the Crimean Peninsula in 2014 and backing pro-Moscow separatists in Ukraine's east.
Pence and Zelenskiy were in Warsaw for commemorations to mark the 80th anniversary of the start of World War II.
U.S. national-security adviser John Bolton said on a recent visit to Kyiv that President Donald Trump could meet Zelenskiy in Warsaw this weekend.
However, Trump cancelled his plans to attend the event in Poland, citing Hurricane Dorian, which is set to make landfall in Florida this weekend.
