CNN, Politico and MS NOW are back in the White House, hours after a federal judge ruled President Donald Trump's ban on the three news outlets was probably unconstitutional and ordered their access immediately restored.

The outlets sought an emergency court hearing to regain entry accusing the White House in a court filing of having "repeatedly violated" the judge's ruling by turning away their journalists. The hearing was called off after access was restored.

Trump initially said he barred the outlets because of "fake news". The White House later cited national security.

But in his overnight ruling, Judge Timothy Kelly cast doubt on the claim about national security concerns.

The chaotic standoff limited some TV coverage as Trump welcomed Chinese President Xi Jinping to the White House ahead of a state dinner later.

In the early hours, Judge Kelly ruled the ban on the outlets should be temporarily lifted because it "likely violated their constitutional due process rights".

CNN, Politico and MS Now all reported being denied entry to the White House on Thursday morning, prompting their request for an emergency hearing.

In response, the director of White House Operations said in a court filing that the press passes and confiscated badges had been restored by 09:45.

Shortly afterwards, all three outlets said they had been allowed back in.

However, networks including Fox News, NBC, CBS and ABC, which pulled out of the White House in solidarity, have yet to confirm they will resume televised coverage.