Otto Warmbier's parents want North Korea added to list of state sponsors of terrorism

— -- The parents of the American student who died after being released from a North Korea prison are looking to get the State Department to add the country as a state sponsor of terrorism.

Twelve senators -- six Democrats and six Republicans -- sent a letter to Secretary of State Rex Tillerson requesting North Korea be added to the State Department's list at the urging of Warmbier's parents. ABC News confirmed the State Department did receive the letter. Among the signatories are both senators from Warmbier's home state -- Ohio Republican Rob Portman and Democrat Sherrod Brown -- and his alma mater University of Virginia -- Virginia Democrats Tim Kaine and Mark Warner.

The bipartisan group asks Secretary of State Rex Tillerson to consider "the totality of North Korea's actions -- including detainment, detention and treatment of Americans citizens," "continued weapons sales and the transfer of sensitive technologies to other state sponsors of terrorism," "a long record of violent and destabilizing acts domestically and internationally," and "its alleged assassination of Kim Jong-name" using a deadly nerve agent known as VX.

USA Today was first to report Warmbier's parents were making the push.

"We have received the letter, are reviewing it, and will respond," a State Department official told ABC News.

There are currently only three countries officially on the State Department's list of state sponsors of terrorism -- Iran, Syria and Sudan. The three countries have all spent decades on the list. Iran was added in 1984, Syria was added in 1979 and Sudan was added in 1993.

North Korea was previously listed as a state sponsor of terror, from January 1988 until 2008, when President George W. Bush removed them as part of an agreement to deal with their nuclear program that later failed.

Warmbier's parents requested North Korea be added to the list in a Fox News interview last month. The State Department said at the time that although they held North Korea accountable for Otto Warmbier's unjust imprisonment, the Secretary of State would have to determine the country provided support for international acts of terrorism to legally meet the standard.

Designation as a state sponsor of terrorism would result in sanctions, including "restrictions on U.S. foreign assistance; a ban on defense exports and sales; certain controls over exports of dual use items; and miscellaneous financial and other restrictions," according to the State Department website.

North Korea is already under very strict sanctions as passed by the United Nations Security Council last month after the country conducted its sixth and most powerful nuclear test.

"This is the strongest set of sanctions that the Security Council has imposed," a U.S. official told ABC News at the time. "It represents yet another major step."

Otto Warmbier died in June just six days after he was evacuated from North Korea upon his release from prison. Warmbier's mother Cindy told Fox News last month that her son returned to the U.S. blind, deaf and "jerking violently" when taken off the plane.

Warmbier spent 17 months in captivity in North Korea. He had been convicted and sentenced to 15 years of hard labor in January 2016 after he stole a propaganda poster.

Warmbier's parents met with Sen. John Cornyn, R.-Texas, on Wednesday, who tweeted a photo and said he supported designating the country as a state sponsor of terrorism.

ABC News' Conor Finnegan and Emily Shapiro contributed to this report.