The US State Department has admitted that President Bush's nominee as UN ambassador gave Congress inaccurate information about an investigation he was involved in.
The acknowledgement came after the State Department had earlier insisted John Bolton's "answer was truthful" when he said he had not been questioned or provided information to jury or government investigations in the past five years.
"When Mr Bolton completed his form during the Senate confirmation process he did not recall being interviewed by the State Department inspector general. Therefore his form as submitted was inaccurate in this regard and he will correct the form," State Department spokesman Sean McCormack said.
Earlier, Senator Joseph Biden of Delaware said he had information Mr Bolton was interviewed as part of a State Department-CIA joint investigation on intelligence lapses that led to the Bush administration's pre-Iraq war claim that Iraq tried to buy uranium from Niger.
Mr Biden, the top Democrat on the Foreign Relations Committee, said that should have been noted on the questionnaire. "It now appears that Mr. Bolton's answers may not meet that standard," he wrote in a letter to Secretary of State Condoleezza Rice.
Mr McCormack also said Mr Bolton was not interviewed in special prosecutor Patrick Fitzgerald's investigation into who leaked the identity of CIA operative Valerie Plame. Earlier in the day, reporters questioned him on whether Mr Bolton testified before the federal grand jury investigating the case, as MSNBC reported last week.
In a letter to President Bush, California Democratic Senator Barbara Boxer said Mr Bolton's admission was "too little, too late" and urged Mr Bush to withdraw the nomination.
"A recess appointment of a man who did not tell the truth to the (Senate Foreign Relations) committee and only admitted the truth when he was caught would send a horrible message," she wrote.
The nomination of Bolton, a favourite of conservatives, has been held up by accusations that he tried to manipulate intelligence and intimidated intelligence analysts to support his views in his position as the top US diplomat for arms control.
The White House is determined to force through the nomination despite not having enough votes in the Senate to ratify his position. It has controversially threatened to appoint him while Congress takes its month-long summer recess which starts this weekend.