WASHINGTON — Sen.-elect Mitt Romney, more than a day away from being sworn in, let the Trump administration know of his disappointment in the president’s leadership and outlined how he plans to conduct himself in the Senate.

In an op-ed published late Tuesday in the Washington Post, the newly elected Utah Republican wrote that while President Donald Trump was not his choice to be the Republican nominee in 2016 he hoped that after his election the president "would rise to the occasion."

“But, on balance, (Trump’s) conduct over the past two years, particularly his actions (in December), is evidence that the president has not risen to the mantle of the office,” wrote Romney, the GOP’s 2012 presidential nominee.

Trump responded to Romney's op-ed Wednesday morning via Twitter:

Romney will be sworn in Thursday, replacing Sen. Orrin Hatch, who stepped down after serving 42 years and urged Romney to run for his seat.

Romney has blasted Trump before. During the 2016 presidential campaign he called then-candidate Trump a "phony" and "fraud" in a scathing speech at the University of Utah. During his Senate campaign, he called out the president’s temperament and character.

Romney did it again in his opinion piece.

“With the nation so divided, resentful and angry, presidential leadership in qualities of character is indispensable. And it is in this province where the incumbent’s shortfall has been most glaring,” he wrote of Trump.

Political observers said the piece in the Post let the White House, party leaders and the public know that Romney won’t keep quiet as a freshman lawmaker.

“Sensationalist pundits may try to turn this op-ed into some suggestion that Mitt is posturing for a potential presidential run. It is not,” said Kirk Jowers, a longtime friend and supporter of Romney. “Mitt’s words today are consistent with everything he has said over the past several years about President Trump.”

Jason Perry, director of the Hinckley Institute of Politics at the University of Utah, said the op-ed answers any lingering questions on whether Romney will be reserved in his opinions.

“What is interesting is that this op-ed was sent to a national news organization. He was clearly attempting to address the nation and the world in some way,” Perry said. “Before his first official day on the job Mitt Romney is already shaping the conversation in Washington.”

Romney didn’t specifically address the most immediate conflict that the new Congress is expected to address on its first day: the partial government shutdown over a standoff between Trump and Democrats over funding the president’s campaign promise to build a wall along the U.S.-Mexico border.

But the senator-elect said he will work with Senate Majority Leader Mitch McConnell, R-Ky., and other senators — and the president — when policies put forward “are in the best interest of the country and my state, and oppose those that are not.

“I do not intend to comment on every tweet or fault. But I will speak out against significant statements or actions that are divisive, racist, sexist, anti-immigrant, dishonest or destructive to democratic institutions.”

He wrote that other nations look to the United States for leadership, but Trump’s “words and actions have caused dismay around the world.” The op-ed cites a Pew Research Center pollthat found confidence in the American president doing “the right thing in world affairs" dropping from 84 percent in 2016 to 16 percent in 2017 among those polled in Germany, Britain, France, Canada and Sweden.

“The world needs American leadership, and it is in America’s interest to provide it,” Romney wrote. “A world led by authoritarian regimes is a world — and an America — with less prosperity, less freedom, less peace.”

He said regaining America’s place of leadership in world politics begins with repairing the political situation “at home.”

“That project begins, of course, with the highest office once again acting to inspire and unite us. It includes political parties promoting policies that strengthen us rather than promote tribalism by exploiting fear and resentment,” Romney wrote. “Our leaders must defend our vital institutions despite their inevitable failings: a free press, the rule of law, strong churches, and responsible corporations and unions.”