Democrat Hillary Rodham Clinton will launch her first television ads of the presidential campaign in Iowa where polls show her in a tight race with rivals Barack Obama and John Edwards, a source familiar with the campaign's strategy told The Associated Press Monday.

Former Gov. Tom Vilsack, who endorsed Clinton's bid for the Democratic nomination after dropping out of the 2008 race, will unveil the new commercials at a news conference, said the source, who spoke on condition of anonymity to avoid pre-empting Vilsack's announcement.

The move intensifies Clinton's campaign in Iowa, her weakest state, and comes on the eve of her latest campaign swing here. Iowa is slated to hold its caucuses on Jan. 14, though the date is certain to change after South Carolina Republicans moved up their primary last week.

Some state polls show Edwards leading while other surveys show Clinton, Obama and Edwards essentially tied. This is in contrast to national surveys and other state polls in which Clinton has a clear advantage. In May, Clinton's deputy campaign manager wrote a memo urging her to bypass the Iowa caucuses to focus time and money on states where she's faring better.

Obama is already airing commercials in the state, and the Democratic candidates are descending upon Iowa this week for photo-friendly appearances at the Iowa State Fair, a high-profile convention of the Iowa Federation of Labor and this weekend's debate sponsored by ABC.

The New York senator was campaigning Monday in Nevada, which follows Iowa in the primary calendar.

It was unclear how much Clinton would be spending on the ads. Ad buyers not connected with the Clinton campaign said her staff had not asked for available time slots or actually placed ads yet with television stations.

That left rivals in the dark about her intentions and the extent of her planned advertising campaign.