As President Donald Trump and his advisers begin weighing replacements for Federal Reserve Chair Jerome Powell, they’re running into one significant complication: It’s not clear that Powell will leave the US central bank next year.

Donald Trump, in a social-media post, said Fed chairman Jerome Powell should “resign immediately.” It was an escalation of his public complaints about Powell, who Trump believes is keeping interest rates high for no reason.

Federal Reserve Chair Jerome Powell said on Tuesday he would not rule out a potential interest rate cut as soon as this month. The remarks come amid a public pressure campaign from President Donald Trump, who has repeatedly urged Powell to slash interest rates.