US Secretary of State John Kerry makes remarks at the State Department in Washington January 21, 2015. [Photo/Agencies]

HAVANA - The United States and Cuba launch talks on Thursday on restoring diplomatic relations after a contentious session on immigration accentuated the difficulties in overcoming half a century of hostilities.

The highest-level US delegation in 35 years will conclude two-day talks in Havana on Thursday, with both sides cautioning an immediate breakthrough was unlikely.

Senior US officials say they hope Cuba will agree to reopen embassies and appoint ambassadors in each other's capitals in coming months.

The United States also wants travel curbs on its diplomats lifted and unimpeded shipments to its mission in Havana.

During talks on Wednesday, the Americans vowed to continue granting safe haven to Cubans with special protections denied to other nationalities.

Cuba complained the US law promotes dangerous illegal immigration and protested against a separate US program that encourages Cuban doctors to defect, calling it a "reprehensible brain drain practice."

As her deputy sparred with the Cuban officials over immigration policy, the lead US negotiator in the diplomatic talks, Roberta Jacobson, arrived in Havana aboard a commercial charter from Miami.