WASHINGTON — Otto Warmbier’s parents have taken their case against North Korea to Washington, pressing lawmakers in private meetings this week to designate that reclusive country as a state sponsor of terrorism.

It’s a cause the Wyoming, Ohio, couple embraced in the wake of their son’s death in June, shortly after he was released from North Korea with severe brain damage. North Korea imprisoned Otto Warmbier for more than a year, detaining the one-time college student as he was preparing to leave that repressive dictatorship.

Otto Warmbier with Sassy, a friend's dog

At the urging of Fred and Cindy Warmbier, 12 senators — six Republicans and six Democrats — sent a letter to Secretary of State Rex Tillerson on Monday, asking him to put North Korea on the list of countries that the U.S. considers sponsors of terrorism.

 “This is something the Warmbiers are very interested in,” said Sen. Rob Portman, R-Ohio, who led the letter along with Sen. Mark Warner, a Virginia Democrat. Other signers include Sens. Sherrod Brown, D-Ohio, Ted Cruz, R-Texas, and Marco Rubio, R-Fla.

More: What 'destroyed' Otto Warmbier? Coroner's report only deepens mystery

Previously: Hometown remembers Otto Warmbier, 'one of our sons.'

The Warmbiers met this week with Portman and Brown, as well as several lawmakers on the House Foreign Affairs Committee. Portman’s office has been helping them arrange meetings with other members of Congress who might be able to help them win this policy change.

North Korea was listed as a state sponsor of terrorism for two decades, from 1988 until 2008. The George W. Bush administration took the country off the list as part of an agreement with North Korea to curb its nuclear weapons program.

“Of course North Korea didn’t follow through on the commitments they had made on the nuclear program, and yet this designation never was renewed,” Portman said in an interview Wednesday. He said North Korea’s dealings with Iran should be enough to justify putting them back on the list, not to mention their recent missile tests and other aggressions.

In their letter to Tillerson, Portman and the other senators note that North Korea has “consistently shown a disregard” for international agreements, “reviving its pursuit of nuclear weapons and the means to deliver them.”

The senators also asked Tillerson to take into account North Korea’s treatment of detained U.S. citizens, although they did not mention Otto Warmbier specifically. Warmbier was in North Korea as part of a tour group when he was detained and charged with hostile acts against the North Korean government.

After a sham trial, he was sentenced to 15 years of hard labor for allegedly stealing a poster from a staff-only section of a hotel in North Korea.

Putting North Korea on the terrorist-sponsor list would give the U.S. another pressure point against North Korea. It would also be a “diplomatic setback” for the country, Marc Thiessen, a former Bush aide and foreign policy expert, wrote in a recent op-ed arguing in favor of the move.

“The additional sanctions that come with a re-designation may not make much of a difference in North Korean’s behavior, but they are one piece of a larger strategy for isolating and squeezing the North Korean regime,” Thiessen wrote.

The State Department declined to comment on the record. For a country to be designated as a state sponsor of terrorism, the secretary of State must determine that the government of that country has repeatedly provided support for acts of international terrorism.

The Warmbiers have not responded to recent requests from The Cincinnati Enquirer for an interview. But in an interview with Fox and Friends last week, they said they were shocked to learn North Korea was not on the terrorist list.

“We owe it to the world to list North Korea as a state sponsor of terror," said Fred Warmbier.

They described in wrenching detail their son’s medical condition upon his return from North Korea. "They destroyed him," said Cindy Warmbier. 

Follow Deirdre Shesgreen on Twitter: @dshesgreen