President Trump began his first full day in the White House by attending the traditional, post-inauguration National Prayer Service on Saturday before visiting the CIA.

The roughly one-hour, interfaith service at the Washington National Cathedral included the National Anthem and a Muslim prayer.

“Hold fast that which is good,” said Bishop Mariann Budde, of the Episcopal Diocese of Washington. “Make no peace with oppression. Strengthen the weak. … Honor all people."

Trump has wasted no time tackling official business -- signing an executive order just hours after being sworn in Friday to ease ObamaCare provisions.

Though a trip to the CIA might seem to come particularly early, a visit to the country’s top spy agency is of particular interest for Trump, considering the tensions between him and the intelligence community following findings about Russia interfering in the 2016 presidential race, at times allegedly to help his candidacy.

Trump last week suggested that intelligence officials leaked an unofficial dossier on him containing embarrassing and highly suspect allegations, and compared the situation to living in “Nazi Germany.”

Outgoing CIA Director John Brennan has denied accusations that he leaked the document and suggested last week to Fox News that Trump lacks “a full understanding of Russian capabilities and the actions they are taking on the world.”

Trump will arrive at the CIA without an agency director.

He appointed Kansas Rep. Mike Pompeo, a fellow Republican, to be the new chief, but Senate Democrats on Friday delayed Pompeo’s confirmation.

The CIA executive director, Meroe Park, is temporarily in charge.

Trump’s and Vice President Mike Pence's visit to the Episcopal cathedral -- which over roughly the past 50 years has hosted President Reagan’s funeral and dozens of other official-Washington events -- also comes with controversy.

Some in the church’s largely liberal congregation have objected to hosting this year’s prayer service.

Budde recently wrote in blog post that she shares "a sense of outrage at some of the (Trump’s) words and actions" but feels an obligation to welcome all people without qualification.

The Saturday service, also attended by the first family and the vice president's family, also included a Navaho Nation blessing and a Jewish prayer.

Also on Friday, Pence administered the oath of office to Defense Secretary James Mattis and Homeland Security Secretary John Kelly, the first members of Trump's Cabinet to clear Senate confirmation.

Asked about his first day as president, Trump said, "It was busy but good -- a beautiful day."

He also signed a proclamation declaring a national day of patriotism, according to a tweet from White House spokesman Sean Spicer.

Though Trump campaigned on a detailed 18-point plan of things to do on Day One, he backed off some of his promised speed, downplaying the importance of a rapid-fire approach to complex issues that may involve negotiations with Congress or foreign leaders. Trump has said that he expects Monday to be the first big workday, his effective Day One.

There are others signs that Trump’s new government is up and running.

Federal websites and agencies immediately began reflecting the transfer of power, and WhiteHouse.gov was revamped for Trump's policy priorities as pages about LGBT rights and the Obama administration's climate change plan were eliminated.

Shortly after Trump became president, the Department of Housing and Urban Development suspended the Obama administration's planned reduction of mortgage insurance premium rates, a move that had been intended to make buying a home more affordable.

More significant policy announcements are expected in the early days of the Trump administration.

Trump's spokesman has said the president intends to withdraw from the 12-nation Trans-Pacific Partnership deal, which he views as detrimental to U.S. businesses and workers. He has also promised to renegotiate the two-decades-old Clinton era North American Free Trade Agreement or withdraw from it.

The Associated Press contributed to this report.