Two U.S. senators who have long pushed to ease restrictions on trade with Cuba say they have put their advocacy on hold in hopes of pressuring Havana to free jailed U.S. government subcontractor Alan P. Gross.

The decisions by Sens. Jerry Moran R-Kansas, and Dick Durbin D-Il., underlined how the case of Gross, serving a 15-year prison sentence, has become a persistent roadblock in almost any attempt to warm up U.S.-Cuba relations.

“I have tried to change the trading relationship with Cuba. I am taking a hiatus from that effort,” Moran told the congressional newspaper The Hill. “I hope that this will put pressure on Cuba to release him.”

Durbin, who as the Senate majority whip is the second-highest ranking Democrat in the chamber, declared that his meeting with Gross in his Havana cell this spring convinced him that more needs to be done to free him, according to The Hill report Sunday

Durbin has been an advocate of using trade to open up closed societies like Cuba, and along with Moran has submitted several legislative proposals over the years to ease the U.S. trade embargo on the island.

Calls to Moran and Durbin’s Washington spokespersons on Monday seeking additional comment for this story were not returned.

Gross, 63, a development specialist working for a U.S. government pro-democracy program, is serving a 15-year sentence for acting against Cuba’s sovereignty when he delivered three illegal satellite phones to Cuban Jews that allowed them independent access to the Internet, bypassing government controls. Cuba has outlawed cooperation with the programs, arguing they are designed to topple the government.

The Obama administration has demanded his release as a humanitarian gesture, arguing that he is in ill health, that his mother has inoperable cancer and that one of his daughters is undergoing treatment for breast cancer.

Havana has made it clear Gross will be freed only in exchange for the five Cuban intelligence officials convicted in Miami in 1998. Four are serving long sentences and the fifth completed his prison term but is on parole somewhere in the United States.

The White House has repeatedly said that it will not swap Gross for the Cuban spies, and that it can make no major effort to improve bilateral relations until the Maryland man is released.

Moran and Durbin, both from farm states, have been trying for years to ease U.S. trade sanctions on Cuba in order to make it easier for the island to buy U.S. food and other agricultural goods — which totaled $347 million in 2011.

Moran has proposed allowing Cuba to make payments directly to U.S. financial institutions, which now must go through third countries. He also wants Cuba, now required to pay for the goods before they leave the United States, to be able to pay once they reach the island.

The proposals have been rejected in Congress, with Cuban-American members and other opponents arguing that easing the U.S. trade restrictions would help the half-century old communist government.

Gross’ case has been making headlines in recent days because of reports that his health is deteriorating. He has lost more than 100 pounds since his arrest in late 2009, and has been serving his sentence in a military hospital in Havana.

His U.S. lawyer, Peter J. Kahn complained last week that Cuba had not given his family the results of his latest medical tests. The U.S. State Department said Thursday it was “extremely concerned” by reports that Gross could no longer walk around his cell.

Cuba’s Foreign Ministry reported Friday that Gross’ health was “normal’’ although he suffered from “chronic conditions typical of someone his age.’’ And over the weekend it sent the medical test results to his family.