U.S. Secret Service director Mark Sullivan told a House committee investigating the Nov. 24 White House security breach that the agency bears full responsibility for mistakenly allowing Tareq and Michaele Salahi to attend a state dinner to which they apparently did not have an invitation. He rejected any suggestion that the White House was to blame.
But when asked if a member of the White House staff stationed at the entry checkpoint could have prevented the Salahis from getting in, Sullivan said "it would have helped."
The Salahis, the accused White House party-crashers who were invited to today's hearing, did not come. Neither did the White House social secretary, Desiree Rogers.
The chairman of the committee, Rep. Bennie Thompson, D-Miss., said he intends to subpoena the Salahis to testify but blocked a request by the committee's ranking Republican, Rep. Peter King, R-N.Y., to subpoena Rogers as well.
"I believe there is a clear distinction here between Ms. Rogers and the Salahis… her role does not encompass security," Thompson said. "It would not be prudent to expend resources in protracted fight with the White House when the testimony sought" is not integral to security of the president.
Earlier, Secret Service director Sullivan acknowledged proper procedures were not followed at one state dinner checkpoint on Nov. 24. He said three agents actually checked a guest list for the Salahis' names and, not finding them there, still allowed the couple to proceed to the next checkpoint inside the White House complex.
"Human error occurred in the execution of our duties," Sullivan said. "A mistake was made. In our line of work, we cannot afford even one mistake."
The agents have been placed on paid administrative leave while the investigation is pending, Sullivan told the committee.
But Sullivan's explanation and acceptance of responsibility failed to placate members of the House Homeland Security Committee who sparred with the director over whether members of the White House staff bore some responsibility too.
"Security is a shared responsibility," said ranking member Rep. Peter King, R-N.Y. "We cannot find any instance where the social secretary's office was not there. In this instance, for whatever reason, a decision was made not to have someone there… not one."
Sullivan said the Secret Service and White House staff agreed during a planning meeting before the state dinner that agents would control the guest list at various entry points.
House Republican Critical Of White House Silence
The committee had called three witnesses to testify on "gate-crash-gate," including White Hosue social secretary Desiree Rogers and the alleged crashers, Tareq and Michaele Salahi.
The Salahis' attorney, Paul Gardner, had said his clients would not attend, and the White House, claiming executive privilege, announced Wednesday that it would shield Rogers from Congress' questions.
"I think, you know, that, based on separation of powers, staff here don't go to testify in front of Congress. She won't. ... She will not be testifying in front of Congress," White House press secretary Robert Gibbs told reporters Wednesday.
That decision drew criticism from some Republicans on the committee, who suggested the White House is acting as if it has something to hide.
Rep. King called Gibbs' "offhand answer" unacceptable.
"I just think they're afraid to take the heat," said King. "They're hiding behind the separation of powers argument, which is not a real argument, and they're stonewalling."
Senior White House adviser Valerie Jarrett refuted those claims on "Good Morning America" today, saying the White House prides itself on transparency and has made the results of its internal review public.
"I think having a full review up on the Web site where anyone can read it is the definition of transparency," said Jarrett. "We think it's important to have a balance and have the White House staff have confidential conversations with the president and his team and not go testify before Congress.
"We think we've really answered the questions fully," she said.
But King, other Republicans -- and even a handful of Democrats -- say the White House is breaking with historic precedent that White House staffers have appeared to answer questions.
"There have been rare examples where White House staff have testified," Gibbs told reporters Thursday. "Watergate, 9/11, Whitewater... I don't think even Peter King would have the audacity to have the Salahis in the trifecta of Watergate, 9/11 or some of the financial hearings."
Obama White House to Place Staffers at Event Entrances
One question still unanswered is why Rogers decided not to have a staff member standing at the entrance to assist the Secret Service in checking guest lists at the state dinner, as has been common practice in previous administrations.
Rogers attended the Nov. 24 state dinner as a guest and told reporters which designer's dress she was wearing.
"Why would you all agree that no person from the White House would be standing there – first of all to greet guests, but at the same time if there were problems, to immediately be able to take care of them?" Rep. Loretta Sanchez, D-Calif., asked Sullivan.
"I would acknowledge that is very rare," Sullivan said. "I believe the memo put out by the White House yesterday -- they recognize that as well.
That memo – by Deputy White House Chief of Staff Jim Messina – instructs Rogers' office to abide by precedent and have a White House staffer present at checkpoints during future official events.
"After reviewing our actions, it is clear that the White House did not do everything we could have done to assist the United States Secret Service in ensuring that only invited guests enter the complex," Messina wrote.
Committee chairman Thompson told reporters Thursday that regardless of whether a White House staffer was present, the Secret Service bears full responsibility.
"The social secretary, they plan parties," he said. "They don't provide security. And I think, to try to say somehow, that individuals who plan parties have the primary responsibility for security is a stretch."
Rep. King, the committee's top Republican, emphatically disagreed.
"I think its wrong. I think it's stonewalling. It was a bipartisan request" to have her appear before the committee, Rep. King said.
ABC News' Pierre Thomas and Dean Norland contributed to this report.