As President Donald Trump’s administration defiantly says it has no authority to order the release of a man it said it mistakenly deported to El Salvador, Sen. Chris Van Hollen said he would travel to the Latin American country to push for Kilmar Abrego Garcia’s return.

In a letter dated Sunday, the Maryland Democrat formally requested a meeting with Salvadoran President Nayib Bukele, who is in the United States this week, “to discuss the illegal detention of my constituent.” Abrego Garcia, a Maryland resident and legal permanent resident of the U.S., is being held in a notorious maximum-security prison in El Salvador.

“I have met with Mr. Abrego Garcia’s wife, mother and brother and, as you can imagine, they are extremely worried about his health, safety, and continued illegal confinement, as am I,” Van Hollen wrote in a letter to Milena Mayorga, El Salvador’s ambassador to the U.S.

In a news release Monday, Van Hollen added that if Abrego Garcia “is not home by midweek,” he planned to travel to El Salvador this week “to check on his condition and discuss his release.” Several other Democratic lawmakers, including Reps. Maxwell Frost of Florida and Yassamin Ansari of Arizona, have said they would be willing to join Van Hollen on his trip.

It’s unlikely that Abrego Garcia will get to leave El Salvador’s Terrorism Confinement Center and return home in the immediate future. Despite a Supreme Court order last week that the administration must “facilitate” Abrego Garcia’s release, Trump officials have argued that his fate is no longer in their hands since he isn’t on U.S. soil. Bukele has similarly expressed helplessness in the matter, saying at the White House on Monday that he doesn’t “have the power” to return Abrego Garcia.

The Trump administration has moved quickly to deport hundreds of people to El Salvador under an 18th-century wartime law, paying the Latin American country approximately $6 million to detain them for a year. Many of their family members have rejected claims that they are affiliated with any gang. Meanwhile, Democrats have sought to highlight Abrego Garcia’s case as an example of the cruelty and chaos of the administration’s immigration policy, as well as its defiance of the judicial branch.