Republican US presidential candidate Donald Trump speaks at a campaign rally in Pittsburgh, Pennsylvania, April 13, 2016.[Photo/Agencies]

WASHINGTON - Republican front-runner Donald Trump took fresh steps to reset his campaign on Wednesday, hiring a top Republican operative and scheduling a meeting between aides and US lawmakers as he girds for a new phase in his White House bid.

Trump is under pressure to professionalize his campaign beyond a close-knit group of advisers and expand the appeal of his anti-establishment candidacy in the face of fierce opposition from rival US Senator Ted Cruz of Texas and a well-funded anti-Trump operation run by establishment Republicans.

Trump announced he had hired Rick Wiley as his national political director. Wiley, a long-time Republican strategist, had been campaign manager for Scott Walker, the Wisconsin governor who dropped out of the presidential race last autumn.

"He brings decades of experience, and his deep ties to political leaders and activists across the country will be a tremendous asset as we enter the final phase of securing the nomination," Trump said in a statement.

In addition, Trump's campaign arranged a meeting in Washington of about a dozen US legislators as the fierce anti-establishment candidate tries to build more relationships inside Washington and broaden his appeal.

The meeting with the lawmakers and senior Trump adviser Ed Brookover is planned for Thursday morning on Capitol Hill, congressional aides said.

About a dozen lawmakers are expected to attend, some of whom have endorsed Trump and some of whom have not but who are interested in his message. Trump will not be there.

A series of policy speeches Trump plans to begin delivering soon could be among the topics discussed, one source said.

"They're definitely planning several policy speeches ... and they are looking for input on those," a Republican source familiar with the situation said.