Obama's Cuba opening hits early obstacles, faces struggle with Congress

(This January 3 story was refiled to correct time element to "half-century" from "half-decade" in third paragraph)

WASHINGTON (Reuters) - Only two-and-a-half weeks after U.S. President Barack Obama announced a historic prisoner exchange and re-establishment of long-broken ties with Cuba, his new policy is encountering obstacles that threaten to flare up when Congress returns next week.