The head of the commission investigating the September 11th attacks has urged the US national security adviser Ms Condoleezza Rice to testify before it in public.
However, the White House has repeated her refusal to do so.
Ms Rice has refused to appear before the independent panel in public and under oath to answer charges from former White House counter-terrorism official Mr Richard Clarke that the Bush administration neglected the threat from al-Qaeda. The White House has asked for a second private session for Ms Rice.
The commission's Republican chairman, former New Jersey Governor Tom Kean, told Fox News Sundayhis panel would continue to press for Ms Rice to appear publicly but would not try to force her to do so under a court order.
"To get into a court battle over a subpoena we don't think is really appropriate right now, nor will it help us," Mr Kean said. "We are still going to press and still believe unanimously as a commission that we should hear from her in public."
But Ms Rice, in an interview on the CBS programme 60 Minutes, said there was "an important principle . . . that sitting national security advisers do not testify before the Congress".
"Nothing would be better, from my point of view, than to be able to testify," she said, according to a transcript of the interview provided by the network ahead of broadcast. "I would really like to do that. But this is a matter of policy."
Mr Clarke, who served under Ms Rice at the White House, has accused President George W. Bush of being determined to go to war against Iraq and of undermining the war on terror by doing so.
Mr Clarke said the invasion a year ago had fuelled anger at the United States and helped the cause of al-Qaeda, blamed for carrying out the September 11th, 2001, attacks on America in which 3,000 people were killed.
The Bush administration has launched a fierce counter offensive against Mr Clarke, whose comments are seen as damaging Mr Bush's attempts to portray himself as a tough anti-terror leader going into presidential elections in November.
Ms Rice told CBS it was "perfectly logical" for Mr Bush to ask his aides on the day after September 11th, as Mr Clarke said he did, if Iraq could have been responsible.