Joe Biden has launched a forceful pushback against the White House, accusing President Donald Trump of fomenting violence, emboldening white nationalism and causing unrest in US cities.

“If I were president today, the country would be safer and we’d be seeing a lot less violence,” the Democratic nominee said in a speech on Monday designed to counter the “law-and-order” message hammered by Mr Trump.

The remarks in Pittsburgh, with the elections just about two months away, was the former vice president’s first major speech on the street violence.

Meanwhile, Mr Trump is threatening to expand federal law enforcement involvement in the western city of Portland, after a person was killed there during chaotic protests over the weekend.

Tweet from @WhiteHouse

On Tuesday, the president will travel to Wisconsin, where police officers shot a black man last week, sparking days of protests.

Unrest saw two people killed by a 17-year-old who may have been aligned with a right-wing militia, looting and arson.

Wisconsin Governor Tony Evers has asked Mr Trump not to come to his state.

“I am concerned your presence will only hinder our healing,” said Mr Evers, a Democrat.

Kenosha, the city at the heart of unrest, has seen several days of relative calm.

On Monday, Mr Trump responded to concerns his presence may reignite violence, claiming his visit could increase “love and respect for our country”.

The president also declined to disavow the actions of Kyle Rittenhouse, the teenager accused of shooting and killing two protesters in Kenosha, saying Rittenhouse was “in very big trouble, he probably would have been killed”.

Heading into a tough election in November, Mr Trump has doubled-down on a message alleging the unrest will only get worse under Mr Biden, noting the incidents are centred in cities run by Democrats.

“If you give violent extremists what they want, the violence doesn’t go away. They gain new power to spread the terror nationwide,” he said during a press conference on Monday.

The Democrats have brushed aside the accusations, with Mr Biden noting Mr Trump is president now and therefore owns the situation.

The speech was seen as Mr Biden acknowledging he needs to be more vocal on the issue of violence.

On top of the unrest, murder rates in some major cities are up this year.

Mr Biden used his speech to talk up support for law enforcement and condemnation of looting after increased attacks from conservatives claiming he is soft on crime and sympathetic towards unrest.

“Rioting is not protesting, looting is not protesting, setting fires is not protesting. None of this is protesting. It’s lawlessness, plain and simple,” Mr Biden said, before shifting to blame Mr Trump for inciting racial tensions.

“Fires are burning and we have a president who fans the flames … We must not burn we have to build,” Mr Biden said, calling the president a “toxic presence in our nation … poisoning our very democracy”.

Mr Biden accused Mr Trump of emboldening white nationalists and failing to understand the protests for social justice or recognise race problems in the country.

One person was killed over the weekend in Portland, with nightly protests there in their fourth month.

He was reportedly a supporter of the president.

Information on the shooter was unclear but there had been tensions between left- and right-wing demonstrators.

The city’s Democratic mayor, Ted Wheeler, blamed Mr Trump for the violence, saying on Sunday the president “created the hate and the division”.

-AAP