WASHINGTON — A Democratic senator has urged President Trump to allow American humanitarian aid workers into North Korea, despite a recent ban on travel to what officials consider a hostile nuclear state but also one of the world’s poorest nations.

The senator, Edward J. Markey, Democrat of Massachusetts and a member of the Foreign Relations Committee, said in a letter dated Nov. 7 that he was “deeply troubled” by reports that the Trump administration was barring aid workers “from shipping supplies or traveling to North Korea as they seek to provide the most basic humanitarian assistance.”

Mr. Markey praised Mr. Trump’s decision to engage in diplomacy with Kim Jong-un, the North Korean leader, but said the aid workers needed to be allowed to do their jobs. Aid groups provide a range of services, including agricultural training and surgery, but are finding it impossible to enter North Korea because of new State Department restrictions.

“The humanitarian situation in North Korea is far too dire for these draconian policies,” Mr. Markey wrote in the letter to Mr. Trump that was also sent to Mike Pompeo, the secretary of state, and Steven Mnuchin, the Treasury secretary.