A flagpole is raised at the Cuban Interest Section in Washington in June in preparation for the reopening of the embassy. Today the U.S. and Cuba restored diplomatic ties.

WASHINGTON — America and Cuba restored full diplomatic relations today after more than five decades of frosty relations rooted in the Cold War.

The new era began with little fanfare when an agreement between the two nations to resume normal ties came into force just after midnight Sunday and the diplomatic missions of each country were upgraded from interests sections to embassies.

Thus end the policy approaches spawned and hardened since President John F. Kennedy first tangled with youthful revolutionary Fidel Castro over Soviet expansion in the Americas. The countries severed ties in 1961.

Maintenance hung the Cuban flag in the lobby of the State Department alongside those of other nations with which the U.S. has diplomatic relations. Cuban officials were to formally inaugurate their embassy in Washington today.

The U.S. Interests Section in Havana had plans to announce its upgrade to embassy status in a written statement today.

Though normalization has taken center stage, there remains a deep ideological gulf between the nations and many issues to resolve, such as disputes over mutual claims for economic reparations, Havana’s insistence on the end of the 53-year-old trade embargo, and U.S. calls for Cuba to improve on human rights.