Eric Cantor, the Republican star unexpectedly bounced from the US Congress by a political novice, said Wednesday he will step down as House majority leader.

"While I intend to serve out my term as a member of Congress from the 7th District of Virginia, effective July 31st I will be stepping down as majority leader," Cantor told reporters a day after his shock primary loss to economics professor Dave Brat.

The move sets off a scramble for the number two post in the House Republican leadership, just as lawmakers crank up their campaigns ahead of November's mid-term congressional elections.

Shortly before addressing reporters, Cantor broke his news to the Republican caucus in a closed-door conference in the US Capitol basement, where lawmakers said House Speaker John Boehner wept as he praised his outgoing deputy.

An internal election to fill the vacuum will take place June 19, said Congressman Tim Huelskamp, who wants to see a conservative win the post.

Cantor was already seen as a conservative leader, but the Tea Party-fueled far-right wing of the caucus is aiming to bring in new blood that could help draw leadership even more to the right.

The outgoing chieftain, the only Jewish Republican in Congress, said Washington was too divided and called for his party to unite, particularly in opposition to President Barack Obama's controversial health care law.

"Truly, what divides Republicans pales in comparison to what divides us as conservatives from the left and their Democratic Party," Cantor said.

Lawmakers have floated three main names as potential Cantor replacements: Kevin McCarthy, who is in line as the chamber's number three Republican, Rules Committee chairman Pete Sessions and Jeb Hensarling, chairman of the House Financial Services Committee.

"I would say that it's wide open," House Republican Phil Gingrey told AFP.

Cantor said he would back McCarthy if he chose to run for the job.

Cantor lost his Virginia district seat to Brat, who was backed by the anti-tax, small government Tea Party movement.

- Cantor will be 'gravely missed' -

Experts and Cantor's colleagues said the majority leader failed to address constituent issues, focusing more on national party priorities and fundraising for other candidates.

Cantor hinted that his attention to leadership concerns may have been a factor.

"There's a balance between holding a leadership position and serving constituents at home," he said.

"But never was there a day did I not put the constituents of the 7th district of Virginia first, and I will continue to do so."

Cantor's loss was widely considered one of the biggest upsets in modern US congressional history.

"I think he's going to be gravely missed," Congressman Mario Diaz-Balart, one of a group of lawmakers trying to hammer out immigration reform legislation, told reporters.

"Anybody who can claim that they can know how this is going to affect any major issue is not understanding what a big tsunami this is."