US President Donald Trump has said that the shooting in Paris that took the life of a police officer would "probably help" far-right candidate Marine Le Pen.

"She's the strongest on what's been going on in France," Trump said in response to her comments on the fatal shooting on the Champs-Elysees, although did not go as far as explicitly endorsing her.

Isis has claimed responsibility for the attack, which came just three days before the first round of the French presidential election.

"[Le Pen's] the strongest on borders, and she's the strongest on what's been going on in France," Trump said in the Oval Office interview.

"Whoever is the toughest on radical Islamic terrorism, and whoever is the toughest at the borders, will do well in the election."

During the same interview, Trump also said that people who were taken to America illegally as children could "rest easy" about his immigration policies.

The former child illegal immigrants, known as "dreamers", were given deportation deferrals under former president Barack Obama's Daca (Deferred Action for Childhood Arrivals) executive order but many have worried that they could be targeted by the current administration's threatened crackdown on immigration.

Trump's comments came after Juan Manuel Montes, a 23-year-old who qualified for deferred deportation, was sent back to Mexico. Trump told AP that the case was "a little different than the Dreamer case" although the news agency did not go into specifics.

As a candidate, Trump came under fire repeatedly for his rhetoric around immigration, including his promise to build a wall along the US's southern border with Mexico.

The administration quickly brought in a haphazard executive order banning citizens of seven Muslim-majority countries before it was struck down in the courts. A revised version is currently held up in similar legal battles.

Trump also told AP that a tax reform package would be unveiled next week and would include a "massive tax cut" for businesses and individuals, "bigger I believe than any tax cut ever," the President said.

Later on Friday, Trump signed a new executive order aimed at financial services which is expected to take another step towards rolling back Obama-era regulations on the sector.