Donald Trump is quickly gaining ground on Hillary Clinton, a national tracking poll released on Saturday shows.

Trump, who was behind the Democratic presidential nominee by 12 points in the ABC News/Washington Post survey just last week, has climbed to within two percentage points, now trailing 47-45 per cent in the same poll.

The poll of 1148 likely voters was conducted before the Federal Bureau of Investigation's revelation to Congress on Friday that it had discovered additional emails related to its probe of Clinton's private email server.

US Attorney General Loretta Lynch advised and objected against FBI Director James Comey's move to send a letter to Congress to inform them about the reopening of the investigation into Hillary Clinton's private email server.


Comey broke from Lynch, who objected to the move along with the Deputy Attorney General Sally Yates, and independently sent the letter to Congress, dropping the bombshell about the restarted investigation based on newly discovered emails, rocking Clinton's campaign.

The probe was triggered while the FBI and New York Police Department investigate allegations disgraced politician Anthony Weiner was once again sexting.

Speaking to CNN, vice president Joe Biden admitted he is "not a big fan" of Weiner.

"Well, oh God, Anthony Weiner,' Biden told CNN's Michael Smerconish. 'I should not comment on Anthony Weiner.

"I'm not a big fan," he continued. "I wasn't before he got in trouble. So I shouldn't comment on Anthony Weiner."

National polls released this week have shown ranging sizes of Clinton's advantage. Surveys by Fox News and Investor's Business Daily each found Clinton up a narrow three percentage points among likely voters, while she led by nine points in separate CNBC and USA Today/Suffolk polls and by 14 points in an Associated Press-GfK poll.

The varying results come as polls capture reactions to a slew of news events, including ranges of enthusiasm among each candidate's supporters and unity among Republicans who have wavered in support for Trump.