WASHINGTON (AFP) - US House Republicans on Wednesday elected Paul Ryan, a youthful, popular and wonkish conservative, as their candidate for speaker of the House of Representatives - a move they hope will unite their fractured camp.

Republican leaders said Ryan, 45, won a closed-door election to become the party's pick to replace Speaker John Boehner, who announced last month he is stepping down on Friday.

"Now it is official, Paul Ryan wins GOP speaker nomination. On to the floor," congressman Bill Huizenga posted on Twitter.

A full vote on the floor of the Republican-controlled House is scheduled for Thursday.

Barring any disaster, Ryan will be elevated to the most important job in Congress, putting him second in the line of presidential succession after the vice president.

Political intrigue however lingers.

Lawmakers leaving the closed-door vote said Ryan had secured only 200 votes in the 247-member Republican conference, leaving him shy of the 218 votes to win outright victory on the floor of the 435-member House Thursday.

But lawmakers expressed confidence that Ryan will secure well above the 218 mark on the final vote.

"I think the overwhelming majority of the conference is ready to move on, and (we are) in the 230s on that," congressman Greg Walden told reporters.

Daniel Webster, who mounted a rebellious bid for House speaker when Boehner announced his resignation, received 43 votes, lawmakers said.