The United States is proud of its partnership with Croatia and is looking forward to strengthening and expanding it in the years ahead, Clinton wrote in the Golden Book upon arriving at the Croatian government.
On her first, one-day visit to Croatia, Clinton will also meet with President Ivo Josipovic and Foreign Minister Vesna Pusic.
A statement from the government will be released after the meeting with Milanovic.
Clinton and Josipovic are expected to address the press.
The secretary of state will wrap up her visit with a dinner organised by Pusic.