Trump willing to invite Putin to White House 'at the right time'

United States President Donald Trump, battling allegations that his campaign colluded with Russians to get him elected, has said he would invite Russian President Vladimir Putin to the White House, but 'at the right time'.

Trump expressed his willingness to invite Putin with reporters travelling with him en route to Paris on Thursday.

It came at a time the scandal reached his eldest son after the American media reported that Donald Trump Jr last year met a Russian lawyer who had promised to provide information damaging to Hillary Clinton, Trump's Democratic rival.

According to the reports, Trump Jr met the lawyer at Trump Tower in New York in June. This week, he released emails about the meeting and the US president publicly defended his son for his 'transparency' in releasing the emails.

Trump has denied allegations his campaign had contacted Russians to tilt the 2016 election in his favour, but the US intelligence agencies have differed with that assessment.

Aboard the Air Force One, Trump, when asked by reporters whether he would invite Putin to the White House, said, "I don't think this is the right time, but the answer is yes, I would."

"Look, it's very easy for me to say absolutely, I won't. That's the easy thing for me to do, but that's the stupid thing to do. Let's be the smart people not the stupid people," he said.

Trump described Russia as 'perhaps the second most powerful nuclear country in the world' and said that if 'you don't have dialogue (with them), you have to be fools'.

Since assuming office on January 20, the Republican president has appeared inclined to do business with Russia.

Trump has previously spoken with Putin by phone, and at the G20 summit in Germany last week, they had their first face-to-face meeting since Trump's election, when he pressed Putin over the election meddling allegations.

Trump twice asked Putin whether Russia tried to hack the election during the meeting and was reportedly appeared satisfied with Putin's denial.

On Thursday, Trump said he wants to make great deals with Russia and added that these deals would affect Moscow.

"Why does that affect Russia? Because Russia makes its money through selling of oil, and we've got underneath us more oil than anybody, and nobody knew it until five years ago. And I want to use it," he said.

"I don't want that taken away by the Paris Accord. I don't want them to say all of that wealth that the United States has under its feet, but that China doesn't have and that other countries don't have, we can't use," he said.

Responding to the allegation that Putin favoured him over Clinton in presidential election, Trump said he would directly pose this question to the Russian president when he meets him next time.

"The next time I'm with Putin, I'm going to ask him: who were you really for? Because I can't believe that he would have been for me. Me: strong military, strong borders - but he cares less about the borders - but strong military, tremendous," Trump said.

Trump said that during his meeting with Putin he did ask him if he hacked the US elections. "I said to him, 'were you involved with the meddling in the election'? He said, 'absolutely not. I was not involved'. He was very strong on it. I then said to him again, in a totally different way, 'were you involved with the meddling'. He said, 'I was not -- absolutely not'".

The US president, though, reiterated that other countries too could have been involved with the hacking of the polls.

"I'm not saying it wasn't Russia. What I'm saying is that we have to protect ourselves no matter who it is. China is very good at this. I hate to say it, North Korea is very good at this. Look what they did to Sony Studios. They were the ones that did the whole deal to Sony," he said.