WASHINGTON - US President Barack Obama holds a narrow lead of 1 percentage point over Republican Mitt Romney as the race for the White House remains effectively tied less than two weeks before the Nov. 6 election, according to a Reuters/Ipsos daily tracking poll released on Friday.

Obama leads Romney among likely voters by 47 percent to 46 percent, well within the online survey's credibility interval. Neither candidate has held a clear lead since shortly after their first presidential debate on Oct. 3.

Some 18 percent of those surveyed already have cast their ballots, as early voting in some form has started in all 50 states and the District of Columbia, the poll found.

The survey of 1,237 likely voters, drawn from a pool of 1,610 registered voters, was conducted between Monday and Friday. The accuracy of Reuters/Ipsos polls is measured using a credibility interval. For this survey, the credibility interval is 3.2 percentage points for likely voters.

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