Pompeo, who served in the Trump administration, said in a letter with John Walters, the CEO and president of the Hudson Institute, a conservative think tank, that protecting Ukraine is connected to issues at home, making the argument as some Republicans, including Johnson, have previously insisted the U.S. must secure the border before sending more aid to Kyiv.

None of our challenges at home will be made better by abandoning our allies at this time of great need, when they are staring down enemies of the free world,” they wrote.

Pompeo has called to support Ukraine before, but the April 1 letter from the conservative Hudson Institute amounts to more pressure on Johnson as Congress returns to work this week to work on a number of pressing issues.