President Trump on Sunday suggested that it was congressional Democrats and their questioning of Michael Cohen that may have led to the outcome of last week’s summit meeting with North Korea.

In a tweet, Trump said: “For the Democrats to interview in open hearings a convicted liar & fraudster, at the same time as the very important Nuclear Summit with North Korea, is perhaps a new low in American politics and may have contributed to the ‘walk.’ Never done when a president is overseas. Shame!”

The summit with North Korean dictator Kim Jong Un was abruptly cut short Thursday after the leaders failed to reach an accord on denuclearization.

Afterward, Trump said, “Sometimes, you have to walk” away from negotiations when they aren’t going well.

The Democrat-controlled House Oversight Committee grilled Cohen, Trump’s former lawyer, for hours Wednesday — the first day of the summit — about his time working for the president’s company. Cohen made claims such as that Trump approved hush-money payouts. Trump has called Cohen a liar.

Cohen’s testimony came before he is set to head to prison in May on tax and campaign finance violations.