The U.S. sanctioned the Iran Space Agency and two affiliated research groups on Tuesday, accusing them of advancing Tehran’s missile programs, following a tweet in which President Donald Trump appeared to mock the failure of an Iranian rocket launch.

The Treasury Department’s Office of Foreign Assets Control said in a web posting that it had added the space agency, the Iranian Astronautics Research Institute and the Iran Space Research Center to its sanctions list.

“The United States will not allow Iran to use its space launch program as cover to advance its ballistic missile programs,” Secretary of State Mike Pompeo said in a statement. “Iran’s Aug. 29 attempt to launch a space launch vehicle underscores the urgency of the threat.”

The launch failed last week when the rocket exploded on its launchpad. Trump later denied in a tweet that the U.S. played any role in the explosion. He included a remarkably detailed image in his tweet that showed the damaged launch site.

Tensions have escalated between the U.S. and Iran as the Trump administration ratchets up financial pressure on the country following the president’s exit from the 2015 nuclear accord.

The explosion came just days after Trump said he’d be willing to meet Iranian President Hassan Rouhani under the “correct” circumstances, and following French President Emmanuel Macron’s decision to invite Iranian Foreign Minister Javad Zarif to join other leaders on the sidelines of the Group of Seven summit in Biarritz.