NEW YORK

U.S. Democratic presidential nominee Hillary Clinton on Friday urged the FBI to resolve an email probe against her "without any delay".

The demand was a bid to ward off attention -- with less than two weeks before the election – from a controversy that has gained new life.

"We are 11 days out from perhaps the most important national election of our lifetimes," Clinton told reporters at a news conference in Des Moines, Iowa. "Voting is already underway in our country, so the American people deserve to get the full and complete facts immediately."

FBI chief James Comey wrote to congressmen earlier Friday to say that emails "pertinent to the investigation" on Clinton were found and being reviewed by agents.

The emails controversy has become the Achilles' heel of the Democratic campaign since it was revealed that the 2009-2013 Secretary of State was using her private email server to correspond with State Department staff, potentially exposing classified information.

"The director himself has said he doesn't know whether the emails referenced in his letter are significant or not," Clinton reassured supporters at the conference. "I'm confident whatever they are will not change the conclusion reached in July therefore it's imperative that the bureau explain this issue in question -- whatever it is -- without any delay."

Republican contender Donald Trump welcomed the development, saying at a rally in New Hampshire: "I have great respect for the fact that the FBI and the Department of Justice are now willing to have the courage to write the horrible mistake that they made."

He was referencing Comey who initially recommended that no charges be brought against Clinton at the end of a months-long FBI probe in July, despite describing her conduct as “extremely careless”.

As the election looms, with voting already underway in parts of the country, most polls suggest a clear Clinton lead, after a series of scandalous revelations and allegations against Republican contender Donald Trump deflated his momentum in September.

Media reports suggest the new batch of emails come from an unrelated investigation into Clinton aide Human Abedin and her scandal-hit husband Anthony Weiner.

The couple separated in late August after Weiner's name was embroiled in a new sexting scandal following two similar controversies that cost him his seat in Congress and a New York City mayoral bid.

Weighing on the news, White House spokesman Eric Schultz said President Barack Obama wants the FBI to make decisions "irrespective of politics".

"[The] president's expectation is that all FBI efforts follow the facts wherever they lead," Schultz said.

State Department spokesman Mark Toner told reporters Friday the agency stood ready to "cooperate to the fullest extent we can" with the investigation, and that it learned of the relaunch of the investigation "when we saw news reports of the letter".

Republican House Speaker Paul Ryan, who is seeking reelection, welcomed the "long overdue" decision and demanded Clinton be barred from intelligence reports.

Clinton "was entrusted with some of our nation's most important secrets, and she betrayed that trust by carelessly mishandling highly classified information", Ryan said. "I renew my call for the director of national intelligence to suspend all classified briefings for Secretary Clinton until this matter is fully resolved."

Comey dismissed pressure last month to reopen the controversial emails probe following its termination in July.

After announcing his decision not to pursue charges, he endured a grilling from House Republicans in a make-or-break moment for Clinton’s bid for the Oval Office.