Maryland: US President Donald Trump said he would make a massive budget request for one of the "greatest military buildups in American history" during a feisty, nationalistic, campaign-style speech in front of eager conservative activists.

Mr Trump used his appearance on Friday at the Conservative Political Action Conference (CPAC), an organisation that gave him one of his first platforms in his improbable journey to the US presidency, to defend his unabashed "America first" policies.

Mr Trump became the first sitting president since Ronald Reagan to address the conference during his first year in office.

Ahead of a nationally televised speech to the US Congress on Tuesday, Mr Trump outlined plans for strengthening the US military and other initiatives, though he again offered few specifics.

He said he would aim to upgrade the military in both offensive and defensive capabilities, with a massive spending request that would make the country's defense "bigger and better and stronger than ever before."

"And, hopefully, we'll never have to use it, but nobody is going to mess with us. Nobody," he said.

He also promised in "obliterate" Islamic State.

With appeals to people on welfare to go to work and pledges to follow through on his vow to build a wall on the US-Mexican border, Mr Trump drew rounds of applause from the large gathering of conservatives, many of them wearing hats emblazoned with the president's campaign slogan, "Make America Great Again."

His speech was heavy on the nationalist overtones from his campaign, focusing on promises to boost US economic growth by retooling international trade deals, rolling back regulations and boosting energy production.

Mr Trump opened the speech with renewed attacks on the media.

He said he considered "fake news" outlets to be "the enemy of the people" and went on to attack many meda outlets as dishonest, accusing them of fabricating sources for stories.

Mr Trump said the media too often relied on anonymous sources.

"They shouldn't be allowed to use sources unless they use somebody's name," he said. 

"Let their name be put out there. Let their name be put out. A source says that Donald Trump is a horrible horrible human being. Let them say it to my face. Let there be no more sources."

About two hours earlier, Mr Trump's own aides had briefed reporters anonymously on White House chief of staff Reince Priebus' discussions with FBI leaders concerning reports about contacts between Trump campaign aides and Russian officials.

Mr Trump himself has disseminated information via his Twitter feed and in speeches that he's attributed to unnamed people.

In his speech on Friday, he pointed to a Washington Post story this month that cited nine current and former intelligence sources who said Mr Trump's former national security adviser Michael Flynn had discussed US economic sanctions on Russia with that country's ambassador before Mr Trump took office.

He did not denounce the story but said he did not believe there had been nine sources.

"They make up sources. They are very dishonest people," he said. "We are fighting the fake news," Trump said. "It's fake, phony, fake."

The Washington Post's stories helped lead to Mr Flynn's resignation after further disclosures that he had misled administration officials, including Mr Pence, over the nature of his conversations.

Mr Trump went on to call the broadcaster CNN the "Clinton News Network", a claim he had previously made on Twitter and during the election campaign.

The new president got a raucous reception from the crowd, which at one point started chanting, "Lock her up" after Mr Trump derided Hillary Clinton, his Democratic opponent in last year's election, for describing some of Mr Trump's supporters as "deplorables."

He went on to mock the presidential campaign of her Democratic rival Bernie Sanders.  

Mr Trump's speech followed several well-received appearances at the four-day gathering by senior members of his administration, including a speech on Thursday night by Vice-President Mike Pence.

Mr Trump's fledgling administration has given conservatives plenty to cheer, including many Cabinet selections and pledges to repeal the Affordable Care Act and pursue sweeping tax reform.

During his speech, he called his victory "a win for conservative values."

The speech marked the fifth time Mr Trump has addressed the conference hosted by the American Conservative Union, but the first as president.

His first appearance in 2011 offered clues to his political ambitions.

"America today is missing quality leadership, and foreign countries have quickly realised this," he said six years ago.

"[The] theory of a very successful person running for office is rarely tested because most successful people don't want to be scrutinised or abused. This is the kind of person that the country needs and we need it now."

On Thursday night, Mr Pence touted the Trump administration's plans to repeal and replace the Affordable Care Act, declaring "America's Obamacare nightmare is about to end."

Earlier in the day, Mr Trump's chief of staff, Reince Priebus, and Stephen Bannon, the White House chief strategist, made a joint appearance. They declared that, contrary to some press reports, they are working hand in hand toward what Mr Bannon described as an unending battle for the "deconstruction of the administrative state."

White House counsellor Kellyanne Conway was also part of the program. During a morning session on Thursday, Ms Conway, the first woman to run a successful US presidential campaign, made headlines by saying that she doesn't consider herself a feminist "in a classic sense" because the term is associated with being "anti-male" and "pro-abortion."

The Washington Post, Reuters