American hopes of opening an embassy in Havana before presidents Barack Obama and Raul Castro meet at a regional summit this week have been snarled in disputes about Cuba's presence on the U.S. list of state sponsors of terror and U.S. diplomats' freedom to travel and talk to ordinary Cubans without restriction, officials say.

The Summit of the Americas will be the scene of the presidents' first face-to-face meeting since they announced Dec. 17 that they will re-establish diplomatic relations after a half-century of hostility. The Obama administration wanted the embassies reopened before the summit starts in Panama on Friday, boosting a new American policy motivated partly by a sense that isolating Cuba was causing friction with other countries in the region.

Arriving at the summit with a deal to reopen embassies in Washington and Havana would create goodwill for the U.S., particularly after it issued new sanctions on selected Venezuelan officials last month that prompted protests from left-leaning countries around the hemisphere.