Hillary Clinton expected to announce presidential run this weekend

The Guardian reported that Mrs Clinton would make her announcement via Twitter at noon on Sunday while en route to Iowa for campaigning, following a similar earlier report in the New York Daily News.

A variety of sources in the Clinton orbit said they were anticipating an imminent announcement but would not confirm the reports.

Mrs Clinton is likely to make her intentions known through a social media announcement followed by campaign travel. This focus on digital communications is an attempt to connect with young voters, who Clinton needs to become American's first woman president.

In her previous presidential run in 2008, Mrs Clinton lost to the current president, Barack Obama, in part because of the Obama campaign's clever use of social media to draw attention to his candidacy and raise huge sums through small donations.

Her campaign is expected to concentrate on making the 67-year-old former first lady relatable to ordinary Americans. Mrs Clinton spent four years jetting to foreign capitals as Obama's first-term secretary of state but has had limited day-to-day contact with everyday Americans.

The announcement will be followed with a series of conference calls setting out her tour details, starting in Iowa, according to the Guardian report.

Mrs Clinton faces no substantial competition, but needs to get her organisation in place for the long battle to come.

Mrs Clinton, the wife of former President Bill Clinton, is the overwhelming favorite for the Democratic nomination and no other major Democratic figure has stepped forward to challenge her, although former Maryland Governor Martin O'Malley has made moves toward a possible campaign.

But Mrs Clinton's biggest obstacle may be overcoming her own image.

She has struggled to get past accusations that she might be too secretive based on the revelation earlier this year that she had gone against federal recommendations to use an official email account while at the State Department and instead used her own private server.

A Quinnipiac University poll released this week had the surprising result that she was even or only slightly ahead of some Republican contenders like libertarian Senator Rand Paul of Kentucky. Most polls in recent months have shown her with a substantial lead over the Republican 2016 field.