President Obama denounced Donald Trump during a press conference Tuesday morning in what is his harshest repudiation of the Republican presidential nominee yet, calling Trump both "unfit" and "woefully unprepared" for the presidency.

"I think the Republican nominee is unfit to serve as president. I said so last week. And he keeps on proving it," Obama said, pointing to Trump's criticism of the Khan family and recent missteps on foreign policy

Trump "doesn't appear to have basic knowledge around critical issues in Europe, in the Middle East, in Asia," Obama said, adding "this is not just my opinion." 

The president went further, calling on Republican leaders to renounce their support for the candidate. He then suggested that party leaders have been hypocritical in criticizing Trump's comments and distancing themselves from him while refusing to publicly withdraw support for him. 

"What's been interesting is the repeated denunciations of his statements by leading Republicans. If you're repeatedly having to say in very strong terms that what he has said is unacceptable, then why are you still endorsing him?" Obama said. "This isn't a situation where you have an episodic gaffe. This is daily, and weekly, where they are distancing themselves from statements he's making ... There has to be a point at which you say, 'Enough.'" 

Only one sitting Republican representative has publicly endorsed Clinton—New York congressman Richard Hanna, who threw his support behind the Democratic nominee this morning. Hanna also called Trump "unfit" to serve the party in the opinion article he wrote for Syracuse.com after announcing his decision to support Clinton.

Obama spoke from the South Lawn of the White House and was joined by Lee Hsien Loong, Singapore's prime minister. The White House is hosting a state dinner Tuesday evening to celebrate the relationship between the U.S. and Singapore.

A spokesperson for the Trump campaign did not immediately return a request for comment, but Trump did upload an ominous, all-caps tweet titled "STATEMENT IN RESPONSE TO PRESIDENT OBAMA'S FAILED LEADERSHIP" with a link to the following Facebook post: