Kaitlan Collins said she was excluded from a Rose Garden event after asking about Russian President Vladimir Putin and Mr Trump's ex-lawyer.

White House press secretary Sarah Sanders said the reporter had shouted questions and refused to leave.

President Trump has repeatedly attacked CNN as "fake news" and has refused to take questions from CNN reporters.

Ms Collins attended a photo opportunity with Mr Trump and European Commission President Jean-Claude Juncker on Wednesday.

She was acting as the White House pool reporter - one of a rotating group of journalists, who will attend an event and write a report which all other networks can use.

This system allows networks to share the burden of covering the president.

Ms Collins said she had tried to ask Mr Trump questions about Russian President Vladimir Putin's postponed visit and recently released tapes documenting a conversation with lawyer Michael Cohen.

The president reportedly ignored the questions. Shortly afterwards, Ms Collins was barred from a Rose Garden press event with Mr Trump and Mr Juncker.

"They said that the questions I asked were inappropriate for that venue," Ms Collins told CNN.

A fight he can win

Anthony Zurcher, BBC News, Washington

Donald Trump's feud with the press is nothing new. Back in 2016 his presidential campaign barred publications from his rallies after they ran critical articles.

Perhaps some thought that, as president, Mr Trump would behave differently. But on this, as in countless other areas, President Trump operates just like Candidate Trump.

In fact, hostilities may be growing. The president bashes the media in speeches and tweets. He refers to a growing number of outlets as "enemies of the American people". He has refused to call on certain reporters during media availability. His press office has limited access to some smaller briefings.

Now an individual reporter has been blocked from a major presidential event - for shouting questions even though the president often answers such call-outs.

The White House says it is frustrated by what it views as reflexively hostile media coverage. It points to instances where reporters got stories wrong or amplified inaccurate reports on social media.

There may be a larger strategy at play, however. Mr Trump often seems intent on needling the media into righteous outrage, focusing their attention inward instead of on stories that could damage his administration.

The public at large doesn't have much sympathy for the journalists these days. The president may feel that a conflict with the media pack is one he can win.
Ms Sanders said a reporter, whom she does not name, has refused to leave after shouting questions, and "was not welcome to participate in the next event" - although colleagues from her network could do so.

CNN condemned the ban as "retaliatory" and "not indicative of an open and free press". The White House Correspondents Association called it "wrongheaded, and weak".

Traditional rival Fox News also attacked the ban.

"We stand in strong solidarity with CNN for the right to full access for our journalists as part of a free and unfettered press," network president Jay Wallace said in a statement.

Fox News chief political anchor Bret Baier retweeted CNN's statement about the ban, saying his network "stands firmly" with the rivals.

Mr Trump is a noted supporter of Fox News, and has appeared on the network for a number of interviews.

The president has publicly criticised a number of major media outlets, notably CNN and the New York Times.

On his visit to the UK, Mr Trump attacked an article in The Sun on the same grounds, although retracted his statement after speaking to a reporter from the paper.