With the White House under increasing attack over the program, the administration also announced that President Bush, Attorney General Alberto R. Gonzales and Lt. Gen. Michael V. Hayden, the former head of the agency, will each give talks next week in support of the program.
The day's events showed the White House's increasingly forceful effort to build public support for the program, as it seeks to demonstrate that Mr. Bush acted within constitutional authority in ordering the agency to monitor international e-mail and phone calls linked to Al Qaeda without seeking warrants.
While the White House usually says it pays no attention to public opinion polls, Scott McClellan, the press secretary, said at a briefing Friday that recent surveys "overwhelmingly show that the American people want us to do everything within our power to protect them."
But several opinion polls this month showed a clear divide over the issue. One poll, conducted two weeks ago by CNN/USA Today, found that 50 percent of those surveyed thought it was right for the president to order wiretaps without warrants and that 46 percent said it was wrong.
With some leading lawmakers voicing increasing unease over the program, Mr. Cheney met at the White House situation room for about an hour Friday morning to discuss it with Congressional leaders.
While officials would not discuss the substance of the briefing, Democratic Congressional leaders were thought to have expressed complaints about the limited nature of the briefings. A nonpartisan Congressional study earlier this week said that the limited briefings might have violated Congressional oversight law, and Democrats are asking that future briefings be opened to all members of the House and Senate Intelligence Committees.
While Mr. McClellan would not discuss Mr. Cheney's briefing, he said: "We have briefed Congressional leaders more than a dozen times. We continue to brief members of Congress in an appropriate manner."
Meanwhile, House Democrats, frustrated that Republican leaders had refused to hold hearings on the matter, held an unusual unofficial hearing of their own on Friday.
The eight Democratic lawmakers at the event were unrelenting in their criticism of a program that they said would open the way to unlimited presidential powers. Some questioned whether Mr. Bush's authorization of it was an impeachable offense.
Several lawmakers and witnesses compared the administration to a British monarchy, casting Mr. Bush as George III. Representative Jerrold Nadler, Democrat of New York, even compared the president's powers to those the Nazis used early to cement their power.
Mr. Nadler said that as he read the broad presidential power claimed by Mr. Bush, "if he were in Germany in 1933, he would not have required the Enabling Act to pass the Reichstag to claim the power," a reference to the law that gave Hitler broad power to run the country.
When asked about the remark, Mr. Nadler's spokesman, Reid Cherlin, said: "He's not comparing Bush to Hitler. He's saying that Nazi Germany is our most extreme example of the rapid expansion of executive power and even there, there was legislative approval of an emergency package."
In a later statement, Mr. Cherlin said Mr. Nadler had "picked an example that he shouldn't have" in illustrating his point.
The White House declined to send anyone to testify at the Democratic event. Representative F. James Sensenbrenner Jr., the Wisconsin Republican who leads the House Judiciary Committee and who has declined to schedule hearings on the eavesdropping program, said the event did not meet Congressional standards because of a "completely one-sided list of witnesses."
While several witnesses brought reputations as liberal critics of the administration, one witness, Bruce Fein, had been a senior Justice Department official under President Ronald Reagan and was critical of the program's legal underpinnings.
Mr. Fein suggested that he would have resigned rather than acquiesce in such a program.
