WASHINGTON — President Trump weighed in for the first time on the massive protests against his presidency that took place in Washington, Boston, and around the globe, stating on Twitter on Sunday that he was “under the impression that we just had an election!’’

His tweet came in response to the more than 1 million people who gathered Saturday for the Women’s March on Washington and other rallies in the United States and abroad in their bid to counter his inauguration the day before.

“Watched protests yesterday but was under the impression that we just had an election! Why didn’t these people vote?’’ Trump asked on Twitter, on a day in which he and his aides mixed unifying messages with a stream of defensive comments.

“Celebs hurt cause badly,’’ Trump added. The enormous event in Washington, which organizers said drew as many as half a million people, was packed with celebrities, including Madonna, Amy Schumer, America Ferrera, and Ashley Judd.

About 90 minutes later, Trump sent a more conciliatory tweet: “Peaceful protests are a hallmark of our democracy,’’ he said. “Even if I don’t always agree, I recognize the rights of people to express their views.’’

On Saturday, Trump and his aides were silent about the protests. Democrats said Sunday that they drew hope from the strong support that the marches received.

Representative Don Beyer, Democrat of Virginia, whose district is heavily Democratic, said he hoped the party could channel the protest energy into political action. If that happens, he said, Democrats could take back the GOP-controlled offices in his state and beyond.

Later Sunday, Trump began rolling out his plans for diplomatic outreach, speaking with Prime Minister Benjamin Netanyahu of Israel by phone and announcing plans for early meetings with Netanyahu and other world leaders.

Trump said he has set up meetings with the prime minister of Canada, Justin Trudeau, and President Enrique Peña Nieto of Mexico.

‘‘We’re going to start some negotiations having to do with NAFTA,’’ he said of his meeting with Mexico, along with immigration and security at the border. Trump has promised to build a wall along the length of the southern border and insisted that Mexico will pay for it.

The president also met with top law enforcement officers to thank them for their service and support. And he swore-in a group of aides, telling them he believed they were ready to rise to a daunting task.

‘‘But with the faith in each other and the faith in God, we will get the job done,’’ Trump said in a ceremony in the White House East Room. ‘‘We will prove worthy of this moment in history. And I think it may very well be a great moment in history.’’

Trump — who on Saturday accused the media of underreporting the crowd size at his swearing-in — boasted in a Sunday tweet that the television ratings for his inauguration were higher than those for former president Barack Obama’s swearing-in four years ago.

“Wow, television ratings just out: 31 million people watched the Inauguration, 11 million more than the very good ratings from 4 years ago!’’ Trump wrote. Nielsen reported Saturday that 30.6 million viewers watched inaugural coverage between 10 a.m. and 6 p.m. on Friday. That figure is higher than Obama’s second inauguration in 2013, which drew 20.6 million viewers. But it’s lower than that of Obama’s first inauguration in 2009.

In talk show interviews on Sunday, Trump’s aides defended the president’s anger at journalists for reporting — correctly — that his inaugural drew a smaller crowd than Obama’s did eight years ago.

Trump counselor Kellyanne Conway said the presidential press secretary, Sean Spicer, had offered “alternative facts’’ from the White House briefing room in which he contested reports on the size of Trump’s inauguration audience.

Conway’s remarks on NBC’s “Meet the Press’’ were challenged by the program’s host, Chuck Todd. “Look, alternative facts are not facts. They’re falsehoods,’’ he said.

‘‘There’s no way to really quantify crowds. We all know that. You can laugh at me all you want,’’ Conway said.

Trump on Saturday declared he believed ‘‘it looked like a million and a half people.’’

There is no official crowd count for the event, but photographs from the same vantage point at about the same time of day clearly show that attendance was significantly less than at Obama’s first inauguration in 2009, when city officials said that 1.8 million people gathered on the National Mall.

Ridership on the Washington’s Metro system also didn’t match that of recent inaugurations, the Associated Press reported.

As of 11 a.m. Friday, there were 193,000 trips taken. At the same hour eight years ago, there had been 513,000 trips. Four years later, there were 317,000 for Obama’s second inauguration.

Trump’s advisers have set Monday up as the president’s first major day of action on his sweeping campaign promises, but as of Sunday night, it appeared as though his team was still making decisions on what moves to make.

Some Republicans had expected Trump to sign more orders over the weekend, but those never materialized.