Former New York City Mayor Michael Bloomberg announced Tuesday he will not run for president in 2020 while also bashing President Trump in an op-ed and pledging to ramp up efforts to solve national issues.

“I’ve never made any secret of my belief that Donald Trump is a threat to our country.” Bloomberg opened his piece, which was published on Bloomberg.com.

Bloomberg believes he could beat Trump in the general election, but acknowledged he would have had difficulty in the Democratic primary.

“I know what it takes to run a winning campaign, and every day when I read the news, I grow more frustrated by the incompetence in the Oval Office,” Bloomberg wrote. “ I know we can do better as a country. And I believe I would defeat Donald Trump in a general election. But I am clear-eyed about the difficulty of winning the Democratic nomination in such a crowded field.”

Bloomberg urged Democrats in the piece to unite through the primary process in order to make sure the best candidate is elected to defeat Trump in 2020.

“It’s essential that we nominate a Democrat who will be in the strongest position to defeat Donald Trump and bring our country back together,” Bloomberg wrote. “We cannot allow the primary process to drag the party to an extreme that would diminish our chances in the general election and translate into ‘Four More Years.’”

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The billionaire mogul also says he did not want to adjust his politics to navigate through a Democratic primary but that he also wanted to do more to combat these next two years of President Trump in office because there is a “likelihood that our biggest national problems will worsen over the next two years.”

“With a leader in the White House who refuses to bring the parties together, it will be nearly impossible for Congress to address the major challenges we face, including climate change, gun violence, the opioid crisis, failing public schools, and college affordability. All are likely to grow more severe, and many of the president’s executive actions will only compound matters,” Bloomberg added.

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Bloomberg said he would devote his efforts and funding to causes such as to climate change and gun control, issues he called “urgent,” and suggested that he could make a bigger impact by not running for the Democratic nomination.

“I’ve come to realize that I’m less interested in talking than doing,” Bloomberg wrote. “And I have concluded that, for now, the best way for me to help our country is by rolling up my sleeves and continuing to get work done.”