President Donald Trump on Tuesday called it “ridiculous” that additional House Democrats considering impeachment proceedings against him, saying they are doing so only because they cannot defeat him at the ballot box.

The president also acknowledged that he had withheld a nearly $300 million military aid package meant to help Ukraine defend against Russia. But on Tuesday he claimed he did so because European countries need to contribute more to Ukraine’s defense.

A number of freshman House Democrats with backgrounds in national security who all had withheld their support for impeachment proceedings penned a Washington Post op-ed Tuesday morning endorsing just that. They said they changed their minds after an intelligence community whistleblower came forward with assertions that Trump had made a “promise” to the newly elected Ukrainian president.

[Trump, Biden offer 2020 preview as president’s team eager to fan flames]

House Speaker Nancy Pelosi of California will meet with key committee chairmen and then with the full Democratic caucus on Tuesday to discuss whether the Ukraine matter is the final straw that will lead them to start a formal impeachment process.

“I think it’s ridiculous,” Trump told reporters as he arrived to address the U.N. General Assembly in New York City.

The president accused House Democrats of moving closer to impeachment because “they can’t stop me” politically, claiming he is leading in polls even though RealClearPolitics’ average of polls show him trailing former Vice President Joe Biden and other leading Democratic candidates, including Sens. Elizabeth Warren of Massachusetts, Bernie Sanders of Vermont and Kamala Harris of California.

Trump has admitted discussing Biden and his son Hunter Biden with Volodymyr Zelensky when he was Ukraine’s president-elect in late July. At issue is Trump’s claim that Joe Biden used his influence as vice president to convince Ukraine’s then-government to end an investigation into a Ukrainian energy firm where Hunter Biden was a board member.

Biden and Democrats on Capitol Hill, echoed by the party’s 2020 presidential candidates, counter that Trump withheld a massive military aid package to Ukraine in an attempt to convince Zelensky to look into the Bidens. Democrats are accusing the president of misusing his power by holding up taxpayer-funded assistance in exchange for a personal political benefit by possibly harming Biden’s chances of securing the Democratic nomination for president.

Several polls show Biden leading Trump nationally and in key battleground states by double digits.

[Analysis: Amid ‘Whistleblowergate,’ Trump again suggests his office has unlimited powers]

“This flagrant disregard for the law cannot stand,” the seven House Democratic freshmen wrote in the Post op-ed. “To uphold and defend our Constitution, Congress must determine whether the president was indeed willing to use his power and withhold security assistance funds to persuade a foreign country to assist him in an upcoming election.”

The op-ed was signed by Reps. Gil Cisneros of California, Jason Crow of Colorado, Chrissy Houlahan of Pennsylvania, Elaine Luria of Virginia, Mikie Sherrill of New Jersey, Elissa Slotkin of Michigan and Abigail Spanberger of Virginia.

The group informed Pelosi of their change of mind and the coming op-ed, Sherrill told CNN on Tuesday morning. Some of Pelosi’s longtime lieutenants within the House caucus on Monday began endorsing an impeachment process.

After Democrats won control of the House in the 2018 midterms, Trump warned them that if their investigations went too far he would go to a “war-like posture” and not work with them on major legislation.

White House Press Secretary Stephanie Grisham and Principal Deputy Press Secretary Hogan Gidley had not returned a reporter’s email asking if work on spending bills, combating mass shootings and lower prescription drug costs would cease if Pelosi decides to move ahead.

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