A U.S. congressional delegation will sit down with Cuban officials on Monday in meetings that may include President Raul Castro, making them the highest-level contacts between the two nations since the declaration of detente last month.

The U.S. delegation is led by Sen. Patrick Leahy, D-Vt., who played a key role in the release of American contractor Alan Gross as part of a prisoner exchange that paved the way for the move toward full diplomatic relations.

Leahy has met with Castro on past trips to Cuba and was expected to do so again on Monday, two days before Assistant Secretary of State Roberta Jacobson arrives in Havana to negotiate the reopening of the U.S. Embassy.

Leahy and five other Democratic senators and representatives are trying to ease the reestablishment of full relations by conveying to Cuban officials that their actions in the coming months will influence Congressional openness to President Barack Obama’s reforms.

But how the Castro government will respond to the U.S. push to expand diplomatic and trade relations is still uncertain.

Cuba has so far offered a guardedly positive reception to Obama’s loosening of the trade embargo on Cuba, saying it welcomes the full package of new economic ties on offer, from sales of telecommunications equipment to exports to the private business sector.

But it insists it will maintain its one-party political system and centrally planned economy.