President Donald Trump is hitting the road to ramp up his long-promised plan to overhaul the nation's ageing airports, roads and railways, in a bid to energise his supporters and distracting from political intrigue in Washington.

Core election promise have been eclipsed by the political furore over Russia's alleged meddling in the 2016 US election.

That drama will come to a head next week when former Federal Bureau of Investigation Director James Comey, who was leading the Russia probe until Trump fired him, testifies before a US Senate panel on Thursday.

Trump - who has denied any collusion between Russia and his campaign - has struggled to keep the spotlight on plans that could give him a political lift. Holding four events next week on infrastructure and jobs will give him the opportunity to provide some counter-programming to the drumbeat of Russia news.

It is a deft messaging move, said Chris Barron, a pro-Trump Republican strategist, who says the president is at his best when he is on the offensive.

"I think we need to see Trump out of DC. I think we need to see Trump out on the road. I think we need to see Trump engaging his base, firing up his base," Barron told Reuters.

During his campaign, Trump promised a 10-year, trillion-dollar program to modernise decrepit infrastructure - a plan that holds bipartisan appeal because of its job-creating potential, and that will require backing from the US Congress.

Legislative wins have eluded Trump thus far. He kicked off his policy push with healthcare and tax reform, initiatives that have become bogged down in process and controversy. The infrastructure push will offer some fresh ideas for the White House and lawmakers alike to discuss.

Trump last month asked Congress for $US200 billion for infrastructure over 10 years, a plan that would encourage state and local governments to lease assets to the private sector to generate funding for other projects.