WASHINGTON - The crowd periodically broke into shouts of "USA! USA!" and "Four more years!" as President Donald Trump drew stark battle lines in his first detailed public remarks on the just-concluded Democratic National Convention (DNC).

"I'm the only thing standing between the American Dream and total anarchy, madness and chaos," the President told the audience at the conservative Council for National Policy, in Arlington, Virginia on Friday morning (Aug 21).

And he warned once again, explicitly, that the Nov 3 election result may not be known for weeks. The Democratic Party was intent on stealing the election, he insisted.

At the DNC, former vice-president Joe Biden and running mate Kamala Harris were sealed as the party's candidates for an election that promises to be the most fraught and consequential in the modern history of the United States, with sharply different visions for the country.

The Democratic Party is equally convinced that he, President Trump, is intent on stealing the election - or will not accept the result if he loses.

The second scenario is deemed very likely by analysts as well. Mr Trump is trailing Mr Biden in polls; many expect that if he loses, it may be a narrow loss.

His remarks - some of his strongest yet - came as the Republican Party readies for its own national convention next week.

He is expected to deliver a speech accepting the nomination next Thursday.

"The Democrats… spent four straight days attacking America as racist and a horrible country that must be redeemed," he charged.

"And yet, look at what we've accomplished," he insisted.

Mr Trump laid out a list of achievements, including building several miles of a wall on the border with Mexico, getting out of the Paris Agreement on curbing climate change and reviving America's oil and gas industry, cutting taxes, and rolling back environmental regulations onerous for farmers.

On the foreign front, he listed the US' defeat of the Islamic State in Iraq and Syria and the killing of its leader, Abu Bakr al Baghdadi; his withdrawal from the Iran Nuclear Deal and killing of Quds Force commander Qasem Soleimani; his moving the US Embassy in Israel from Tel Aviv to Jerusalem; recognition of Israeli sovereignty over the Golan Heights; and this month's deal between Israel and the United Arab Emirates.

And the administration has taken "historic action to stand up to China's trade cheating and plundering", he said.

If Mr Biden won, China would "own" the US, he charged.

The President accused the Democratic Party of being anti-religion, bent on taking away the constitutional right to bear arms, defunding or abolishing the police, and of "tearing down America".

"The future of our country, and indeed our civilisation, is at stake on November 3rd," he said, painting a grim picture of a Biden presidency pulled to the far left by radicals in the Democratic Party who would raise taxes and be weak on crime and borders and immigration.

"It will be a totally different country… and ultimately, it will fail," he said. "Economically, it can't work. We'll go into a depression… your stocks will crash."

Focusing on the vulnerability of mail-in ballots to fraud, he told the audience: "You're not going to be able to know the end of this election, in my opinion, for weeks, months - maybe never.

"Once you go past the first week, you're never going to know."

It is a theme he has repeatedly emphasised, citing 51 million mail-in ballots that he maintains are being sent to voters, some of whom do not exist.

Some states have universal mail-in ballots, now more important, given the risks of mingling at polling booths in the pandemic.

There have been some issues with them: In Nevada, for instance, Clark County mailed ballots for its June primary election to all its registered voters, but 223,000 were never delivered.

Hundreds of thousands had the wrong addresses, according to a report from the right-leaning Public Interest Legal Foundation.

But the figure of 51 million cited by the President remains hotly debated.

The Democratic Party is in favour of and wants expansion of mail-in balloting, which has been standard practice in American elections.

But Mr Trump has seized on this, thus discrediting the process, and reinforcing fears that he will not accept the result of the election if he loses.

"It will be a tremendous embarrassment to our country,'' he said. "It'll go on forever, and you'll never know who won.

"What's going to happen?" he said. "They're going to be taking them and hiding them.

"So I say that for you, I say it for the cameras… I will tell you that this is a very serious problem for a great democracy.

"This is a very, very serious problem, and something has to be done about it," he warned.

And directly addressing the media in the room, he said: "I say this for the media: This will be the greatest catastrophe - one of the greatest catastrophes in the history of our country. That's how serious it is.

"And they also think I'm trying to steal an election. Just the opposite: I want the fair results of an election."