Hillary Clinton's speech: "Humbled and more than a little surprised"

Speaking at the upstate farm of current New York Senator Patrick Moynihan, Mrs Clinton pledged to be a "strong and effective advocate on behalf of the people of New York."

"I care deeply about the issues that are important in this state that I've already been learning about and hearing about," she said.

Among them, she said, were creating jobs throughout the state, and providing quality education and health care.

She was immediately asked to address criticism that she is a "carpetbagger" for choosing to seek election from a state where she has never lived or worked.

"What I am for is maybe as important, if not more important, than where I am from," Mrs Clinton said.

Her most likely opponent in the contest for the Senate is the current mayor of New York City, Rudolph Giuliani.

Senate race of the century

Stephen Sackur in New York State: "Hillary Clinton has moved centre stage"

Polls indicate that support for the First Lady and the mayor is almost evenly divided.

The contest is already being billed as the most gripping Senate race since Abraham Lincoln was defeated by Stephen Douglas in 1858.

Mrs Clinton's campaign announcement marks the start of a four-day "listening tour" of central New York State.

"I'm going to be listening very hard," she said. "I'm going to be learning a lot."

Later in the week she will visit Cooperstown, Utica, Syracuse and the state capital, Albany.

Campaigning begins

Support for Mrs Clinton is stronger in New York City, where Democrats outnumber Republicans five to one, while support for Mayor Giuliani is greatest in upstate New York.

The mayor has yet to declare formally that he will run, but he has been seeking funding from Republican Party activists.

Mr Giuliani's campaign has already tried to cast Mrs Clinton as an outsider, unfamiliar with the state and the needs of New Yorkers.

His devoted support for the New York Yankees is being favourably compared with the First Lady, who roots for both the Yankees and the rival Mets.

She has also been lambasted for her belated invitation to the Yankees to visit the White House - eight months after their latest World Series victory.

Republicans are bound to make the most of all such gaffes. They are already arranging for her to be met by people dressed as insects - a reference to a remark made by a Clinton aide, who said the couple would not holiday in the "fly-infested" Adirondacks.

Mr Giuliani, who is serving his second four-year term as New York City mayor, is barred from seeking re-election to that post after his term expires in 2001.