Cuba's President Raul Castro (R) and U.S. President Barack Obama (L) attend a press conference at the Revolution Palace in Havana, capital of Cuba, on March 21, 2016. (Xinhua/Joaquin Hernandez)

HAVANA, Aug. 1 (Xinhua) -- The Cuba-U.S. talks on settling multibillion dollars of claims made against each other are one of the most "complex and difficult" negotiations in their normalization process which started last year, a senior Cuban official said Monday.

Havana and Washington last week concluded a "substantive" second round of talks in the U.S. capital after the first meeting in December outline their respective claims as part of a deepening detente.

"It is an issue of very high complexity, with difficult political, technical and legal aspects that is only in its initial stage," Cuba's Deputy Foreign Minister Abelardo Moreno told local press.

Washington is seeking a compensation of 10 billion U.S. dollars, mainly for properties nationalized in Cuba after its 1959 revolution led by Fidel Castro.

Alfonso Munera (L), Secretary General of the Association of Caribbean States (ACS), and the Cuban Deputy Foreign Minister Abelardo Moreno (C), take part in the 7th Summit of the ACS, in Havana, Cuba, on June 2, 2016. (Xinhua/Emilio Herrera/Prensa Latina)

Havana, meanwhile, is seeking at least 300 billion U.S. dollars in claims for economic costs of the U.S. trade embargo on Cuba.

"Both sides exchanged information on their respective claims, legal and technical aspects as well as basic information on each case with the goal of preparing the process of negotiation," said Moreno who also headed Cuba's delegation to the talks.

He said that both sides will continue in the coming months to hold meetings on the issue but added that Cuba will not rush the talks.

"We are talking about a process in two directions, Cuba will not accept unilateral solutions," he noted.

Cuba and the United States re-established diplomatic relations a year ago, ending decades of hostility.

The two nations have since signed agreements on the environment, mail services, security and direct flights. However, thorny issues like claims, democracy and human rights were barely touched during talks.