US Democratic presidential nominee Hillary Clinton holds a Halloween mask while joking with her staff on her campaign plane in Erlanger, Kentucky, US October 31, 2016. [Photo/Agencies]

WASHINGTON - The US Justice Department said Monday that it will try to reach a quick conclusion of the latest probe into Democratic presidential nominee Hillary Clinton's emails.

Assistant Attorney General Peter Kadzik assured Congress in a letter that his department "will continue to work closely with the FBI and together, dedicate all necessary resource and take appropriate steps as expeditiously as possible."

The pledge came after FBI director James Comey said Friday new evidences relating to Clinton's private email server are being assessed.

Comey's announcement drew criticism from Democrats who accused him of not following the tradition of keeping investigations from the public's sight 60 days before presidential elections.

The White House defended Comey Monday, with press secretary Josh Earnest saying President Barack Obama does not believe that Comey was intentionally trying to sway the election.

Clinton on Monday played down the damage of the probe, telling a rally in the swing state of Ohio that "there's no case here" and that she's confident no charges will be made.

Seizing on the investigation, Republican candidate Donald Trump warned Monday that if Clinton were to be elected, the country would face a "constitutional crisis."

Benefitting from the email controversy, Trump narrowed the gap with Clinton by gaining 2.4 percent in the polls over the weekend, according to an average of major polls calculated by RealClearPolitics.