Donald Trump has blamed his predecessor for anti-Trump rallies nationwide and suggested Barack Obama had something to do with embarrassing leaks from the White House.

In a wide-ranging interview with Fox News' Fox and Friends show ahead of his first speech to Congress, the President laid the blame on Mr Obama for mobilising those against him.

He also gave himself an A+ for effort in his first weeks as President, but marked himself down for his political messaging "a C or C+".

"I think President Obama is behind it because his people are certainly behind it and some of the leaks possibly come from that group which are very serious leaks because they're bad in terms of national security, but I also understand that's politics."

The White House has been trying to crackdown on leaks coming from the Trump administration, partly led by press secretary Sean Spicer.

Details of a secret meeting were leaked to media shortly after Mr Spicer brought his communications team in to warn them about leaking information.

They reportedly had their personal and government-issued phones checked in the presence of lawyers.

An unnamed source told Politico Mr Spicer was unhappy with the information which had been passed to media from a planning meeting.

Mr Trump said he was "okay" with the way Mr Spicer was trying to stem the leaks and how he handled the phone checks.

However, he would have done it differently.

"I would have gone one-on-one with different people."

Asked if he'd check their phones during that meeting, he said it would have been a possibility.

"There's a hell of a lot of worse than that, I'll be honest with you."

He said he wouldn't be surprised if his theory about Mr Obama was true.

"I understand how the world works - that's politics. I'm changing things he's wanted to do."

That includes changing the Affordable Care Act, often called Obamacare.

The plan, in part, allowed those with pre-existing medical conditions such as Alzheimer's disease, HIV and epilepsy, to get insurance coverage.

It is estimated to have allowed around 22 million people to get insurance coverage.

"We have a really terrific, I believe, healthcare plan coming out, we have to understand Obamacare has been a disaster, it's way out of control, it doesn't work."

Mr Trump also addressed his decision not to attend the White House Correspondents' dinner a tradition for presidents past which gives them a chance to show off their humorous sides.

He said the rise of "fake news" was partly behind the decision.

"Over the years you make a mistake, I fully understand when they [criticise] you, but when they make stories up, when they create sources, because I believe that sometimes they don't have sources, that the sources don't exist, and sometimes they do exist, I'm not saying all sources, but I believe a lot of the sources are made up, a lot of the stories are made up, I believe a lot of the stories are pure fiction - they just pull it out of air.

"I just thought in light of the fact of fake news and all these things we're talking about now I thought it would be inappropriate."

But he didn't rule out possibly attending in the future.

"I have great respect for the press, for reporters and the whole profession, with all of that being said, I thought it would be better if I didn't do the dinner that doesn't mean I won't do it next year."

All eyes on Congress speech

After a turbulent start to his presidency, Mr Trump is set to go before Congress to give a speech that will be closely watched for details of his plans for the economy and whether he can strike a more conciliatory tone.

World financial markets will be scrutinising the Tuesday night (local time) address in the House of Representatives for specifics of how the Republican president aims to make good on promises to tackle tax reform, boost infrastructure spending and simplify business regulations.

White House officials say the speech will include some gestures toward unifying a country polarised by a bitterly fought election and divided in the early days of his presidency.

An average of recent polls by Real Clear Politics put his approval rating at about 44 percent, low for a new president.

Mr Trump has signed a flurry of executive orders, pulled the United States out of a Pacific trade deal and nominated a conservative judge, Neil Gorsuch, to fill a vacant position on the Supreme Court. But his first month has been characterised by missteps, internal dramas and acrimonious disputes with the news media, and he has yet to score any legislative accomplishments.

The President's party controls both the House and Senate, giving him a chance to reshape the economy with lawmakers. He faces a host of questions going into his first speech before a joint session of Congress.

Specifics of his plan to overhaul former President Obama's signature healthcare law have not been released. He has yet to describe how to pay for a sharp increase in planned spending on rebuilding US roads and bridges.

His proposals to cut taxes for millions of people and corporations have not been sketched out. His strategy for renegotiating international trade deals remains unclear. He took delivery on Monday of a Pentagon proposal for fighting Islamic State militants and must decide on it in the days ahead.

Trump seeks a big increase in defence spending but that plan includes a demand that non-defence federal agencies cut funds to offset the cost, painful reductions likely to face opposition in Congress.

Trump's lack of legislative success so far contrasts with most of his recent predecessors, though not all of them.

Trump's travel ban, which he says was needed for national security reasons, caused wide disruption at airports, sparked protests and was blocked by a federal court. He is expected to sign a replacement order on Wednesday (local time).

Democratic lawmakers plan to attend the speech. But at least one, Representative Luis Gutierrez of Illinois, has said he will protest Trump by refusing to applaud or give him a standing ovation, as is a custom at presidential speeches.

Reuters / Newshub.