Secretary of State John Kerry paid his respects to those killed during the unrest that led to the overthrow of Ukrainian President Viktor Yanukovych during a visit to Kiev's Independence Square on Tuesday.
Kerry arrived for talks with the new government amid tensions with Russia, which took control of the strategic Crimean Peninsula over the weekend.
He visited the Shrine to the Fallen, one of the memorials established after snipers targeted protesters in Kiev.
He met with religious leaders and laid flowers at the shrine, which was erected for the more than 80 protesters the new government says were killed in demonstrations against pro-Moscow Yanukovych.
Reuters quoted Kerry as describing his visit to Kiev as "moving, distressing and inspiring."
Kerry is expected to spend time with senior Ukrainian officials, including the country's new prime minister and acting president, as well as members of the parliament.
Kerry is also due to travel to Paris and Rome this week.
The Associated Press and Reuters contributed to this report.