It comes just as the Republican candidate had gone on the offensive over the subject of planned debates between himself and Vice-President Al Gore.
By US affairs analyst Gordon Corera
If his remark about a New York Times reporter was the first time George W Bush had been caught with his pants down verbally, people probably would not mind too much.
But he is the candidate who called people from Greece, Grecians and who refers to ''tariffs and barriers'' as "terriers and barriffs".
And both the timing and the substance of his latest gaffe are deeply unfortunate for him.
It comes just as the Republican candidate had gone on the offensive over the subject of planned debates between himself and Vice-President Al Gore.
Mr Gore had previously said he would debate Mr Bush anytime, anywhere and Mr Bush was claiming that his rival had backed down.
Face-to-face
He claimed that the vice-president's promise was an example of "Washington double-speak", allowing him to return to his theme that "it's time to get some plain-spoken folks in Washington, DC."
But the off-colour comments about a reporter merely helps turn the spotlight back onto Mr Bush.
This raises questions about how he would perform in debates and whether it is Mr Gore or Mr Bush who is running scared from in-depth, face-to-face confrontations.
Debates are always important but this year they are more important than ever, with such a close race.
Gore's debating skills
There is no requirement that candidates for the presidency debate with each other during the general election, and so it is left to the two candidates to negotiate some kind of agreement.
A framework has been put forward by a non-partisan commission on presidential debates, which involved three match-ups (and one for the vice-presidents) in October.
But, while Mr Gore has said he will participate in these, Mr Bush has put forward his own plans. These include debates on specific TV shows which would probably only be carried by one network and would have a considerably smaller audience.
The official debates organised by the commission reached audiences of more than 90 million in 1992, and even though this dropped to more like 40 million in 1996, this is still nearly double the number who watched each of the conventions.
Under the plan Mr Bush has proposed, there is little chance of such a big audience and the confrontation on these shows would also be less formal and easier on the candidates.
Everyone knows that Mr Gore is a formidable debater.
He demolished Ross Perot in a debate on the North American Free Trade Agreement and comfortably beat Republican vice-presidential candidate Jack Kemp in 1996 with his relentless, ruthless approach and mastery of fact and detail.
Logged on the web
Meanwhile, Mr Bush is relatively unproven, although also often underestimated.
Websites have pages devoted to Bushisms - occasions when the candidate got his words muddled.
Most recently he warned that: "We cannot let terrorists and rogue nations holds this nation hostile or hold our allies hostile."
Other one-liners include: "I understand small-business growth - I was one."
A serious gaffe in a debate could be fatal for Mr Bush since it plays to his greatest weakness - the fear that he is not up to the job and does not have enough substance or experience.
And so Mr Bush's latest gaffe may have only increased the sense among his supporters that a big audience is exactly what he needs to avoid.