WASHINGTON, USA (AFP) — The United States said yesterday that it has denied two Cuban diplomats in Washington permission to visit New York because envoys at the US mission in Havana are barred from leaving the Cuban capital.

The deputy chief of mission and the first secretary of the Cuban interests section asked permission to travel "to New York to participate in the Marxist Leninist Today Forum," State Department spokeswoman Victoria Nuland said.

"Now we certainly have no objections to the reason for their travel. However, we denied the visas because they have not been allowing our guys in Havana to leave the city at all," Nuland told reporters.

When he entered office in January 2009, US President Barack Obama raised hopes that ties with the Americas' only one-party communist regime would improve dramatically, but very little progress has been made.

Relations only worsened when Cuba last year sentenced US contractor Alan Gross to 15 years in prison for trying to distribute satellite phones and computer equipment to members of Cuba's Jewish community.

For the last 50 years Cuba has been subject to comprehensive US economic sanctions.