GLEN JEAN, WEST VIRGINIA (REUTERS) - After another challenging day in Washington, United States President Donald Trump flew to West Virginia to a field full of 40,000 chanting and cheering Boy Scouts, telling them he was happy to leave Washington behind.

"Who the hell wants to speak about politics?" Mr Trump boomed, telling the boys he wanted to talk about how to achieve their dreams.

But politics proved too hard for Mr Trump to resist on a day he spent pleading for Republican senators to vote to advance his long-promised healthcare overhaul and watching his son-in-law Jared Kushner being grilled on Capitol Hill about contacts with Russia.

It did not take long for Mr Trump to veer from inspiration to denigration.

The teenaged boys loved it, cheering wildly at each sick burn, hooting and hollering like they were at a wrestling match.

"Tonight, we put aside all of the policy fights in Washington, DC, you've been hearing about with the fake news and all of that," he told the boys, sitting state by state in brightly coloured T-shirts.

"You know, I go to Washington and I see all these politicians and I see the swamp and it's not a good place," said Mr Trump. "In fact, today I said we ought to change it from the word 'swamp' to the word 'cesspool' or perhaps to the word 'sewer'. It's not good. I see what's going on and, believe me, I'd much rather be with you, that I can tell you."

He told the boys that the media were dishonest and would not show the size of their jamboree on television. "Fake media, fake media," Mr Trump said, eliciting a chorus of boos and cheers.

He recounted his election-night victories, state by state, the boys from Wisconsin cheering when they heard their state mentioned, the boys from Michigan doing the same.

But the most sustained round of cheers and jeers came when Mr Trump mentioned his predecessor President Barack Obama, who had declined invitations to speak to the scout gathering while he was in office. "By the way, just a question: did President Obama ever come to a jamboree?" Mr Trump said.

Mr Trump said he has 10 former Boy Scouts serving in his Cabinet and White House and brought a few on stage as examples of Boy Scout leadership in action, including Mr Tom Price, his health secretary.

"Hopefully, he's going to get the votes tomorrow to start our path towards killing this horrible thing known as Obamacare," Mr Trump said, referring to Mr Obama's signature healthcare legislation, as the boys booed.

"He better get them, otherwise I'll say, 'Tom, you're fired,'" he said, borrowing the catchphrase from his reality television show, The Apprentice.