Sen. Elizabeth Warren is asking Secretary of State Marco Rubio for information on the Trump administration’s contingency plans if billionaire Elon Musk breaches his companies’ current contracts with the U.S. amid the ongoing public fall out between him and President Trump.

In a letter to Rubio as acting national security adviser and obtained by CBS News, Warren said Mr. Trump and Musk’s public disagreements about the upcoming reconciliation bill that escalated into a public online spat could “have serious implications for U.S. national security.”

The Massachusetts Democrat mentioned Mr. Trump’s proposal to terminate Musk’s government contracts and subsidies, which the world’s richest man followed with a threat that SpaceX would “begin decommissioning its Dragon spacecraft immediately.” Musk has since walked back his threat.