HAVANA - US and Cuban officials met Monday in Havana for new talks on restoring diplomatic ties, but their historic rapprochement was marred by tensions over Venezuela.

The top US diplomat for Latin America, Roberta Jacobson, met her Cuban counterpart Josefina Vidal behind closed doors for a third round of talks on normalizing relations, but the atmosphere of reconciliation was marred by protests over Washington’s treatment of Venezuela.

As Jacobson touched down in the Cuban capital late Sunday, thousands of people attended a concert and rally to “support the Bolivarian (Venezuelan) people and government” in their mounting row with the United States. US relations with Venezuela, a key Cuban ally, have been on a downward spiral since Venezuelan President Nicolas Maduro accused Washington in February of sponsoring a coup attempt against him.

His government arrested several people in the aftermath of the allegation, including the opposition mayor of Caracas.

US President Barack Obama responded by imposing new sanctions on seven senior Venezuelan officials, accusing them of cracking down on the opposition.

He called Venezuela an “extraordinary threat to the national security” of the United States - language Maduro said showed the US was itself an “imperialist threat.” The socialist leader then ordered “defensive military exercises” and asked Venezuela’s National Assembly to grant him the power to rule by decree on defense and public safety matters - a request voted through by his legislative majority Sunday.

The escalation has exposed the gaps that still remain between the United States and Cuba, which relies heavily on Venezuelan oil money since the collapse of the Soviet Union. Cuba’s communist government called Obama’s new sanctions “arbitrary and aggressive.”

The concert on the steps of the University of Havana was a show of solidarity with the Venezuelan people’s “suffering under the recent aggressive (US) escalation,” an organizer told state-run newspaper Juventud Rebelde.

Unlike the previous two rounds of talks held since the historic US-Cuban rapprochement was announced on December 17, no press conference was scheduled for this week’s meetings between Jacobson and Vidal, Cuba’s top diplomat on US affairs.

A senior State Department official downplayed expectations of the talks, due to last until mid-week, saying they will probably not produce any major announcements.

Both sides are trying to iron out remaining issues with an eye on the upcoming Summit of the Americas in Panama on April 10-11. President Barack Obama is due to attend the summit, where Cuba will also participate for the first time.

Obama has said he hopes the two countries can reopen embassies in each other’s capitals before the summit. “That’s something that we still would like and that’s what we hope,” the senior State Department official said.

He said Washington was “disappointed” with Cuba’s position on its row with Venezuela, but that “it will not have an impact on these conversations moving forward.” But the two sides remain at odds on several thorny issues, such as compensation for American property nationalized after the Cuban Revolution, freedom of movement for diplomats and Cuba’s removal from the US blacklist of state sponsors of terror.

The two sides are next due to meet in late March, when they will address the delicate issue of human rights for the first time.