Mayor Bloomberg has been asked many times whether he harbors presidential aspirations. Yesterday may be the first time he was asked the question under oath.

Mr. Bloomberg spent the day sitting for a deposition in a civil lawsuit, the first time he has done so as mayor. The defamation case against the mayor was brought by a South Carolina gun salesman who claims the mayor spoke ill of him in the press. The deposition lasted the entire workday, and the topics ranged from Mr. Bloomberg’s views on the Second Amendment to whether he intended to run for president.

Regarding a possible presidential run, a lawyer for Mr. Bloomberg told him not to state his current plans, but to speak only of his mindset in spring 2006, according to a video of the deposition viewed by The New York Sun.

“I was not planning to run for president then,” Mr. Bloomberg said. The 2006 date was used because it was around the time the South Carolina gun dealer, Larry Mickalis, first learned of the statements the mayor made about him, and it is the time frame at issue in the suit.

“I was never at that period of time — in the period I was instructed to be able to answer — considering running for president,” Mr. Bloomberg said.

Lawyers for both sides spent several minutes arguing over whether Mr. Bloomberg would answer whether he was “planning to run for president as you sit here today.” The question was posed by attorney Carl Pierce II of Charleston, S.C. It is not clear which lawyer was speaking for the mayor. Several lawyers representing him were in the room, including the city’s corporation counsel, Michael Cardozo, and Kenneth Taber of Pillsbury Winthrop Shaw Pittman LLP. In the end, the mayor did not answer it.

At another point, Mr. Pierce asked Mr. Bloomberg about his understanding of the Second Amendment. Over the objection of a lawyer, the mayor responded: “I believe the Second Amendment of the bill of rights gives you the right to keep and bear arms. I also believe courts have held over the years that government does have the authority to limit these rights in situations when the public is in danger. For example, carrying concealed weapons in big cities.”

At another point, Mr. Bloomberg talked of his own experiences with guns, including the .22 rifle his mother bought for him while he was a boy scout. He also said he had been handed a gun on one or two occasions at FBI ranges, but could not recall whether he fired it.

The lawsuit at issue stems from an investigation by the city into whether certain out-of-state gun dealers were responsible for a disproportionate number of crime guns recovered in New York City. The investigation included a sting operation in which private investigators tried to make straw purchases at several gun shops, including Mr. Mickalis’s.

Mr. Mickalis, along with two other attorneys, Sonaly Hendricks and Justin Kahn, were present for the deposition. At one point in the deposition, Mr. Pierce invited the mayor to have Mr. Mickalis arrested if the mayor believed the gun dealer had committed a crime. The mayor did not order any such arrest.

At one point, Mr. Bloomberg said that “as far as I know” the city was paying for the Web site of the “Mayors Against Illegal Guns” coalition, which Mr. Bloomberg played a leading role in founding. The coalition has brought significant national attention to Mr. Bloomberg.

The mayor said the press he has received for the venture has not necessarily been good for his national image, hinting at the enmity he has engendered from gun rights groups.

“Generally people would say it’s not good politics, but politics had nothing to do with it,” Mr. Bloomberg said of the organization.

Mr. Pierce, following the deposition, described the mayor as “collegial.”

“I think he made a big effort to be friendly,” Mr. Pierce said.

During the deposition, Mr. Bloomberg did not discuss his assets beyond saying he was a billionaire. He added, “The papers say that I am a very wealthy person.”

At one point, Mayor Bloomberg quipped to the room full of lawyers: “I never wanted to be a lawyer.”

Mr. Pierce replied: “That might get you elected president.”

Mr. Bloomberg smiled and pursed his lips.