The Bush administration expects a possible diplomatic backlash after it conceded that it used British territory to transport suspected terrorists on secret rendition flights despite repeated earlier assurances that had not happened. US officials have sought to quell the fallout by apologizing to Britain for what they said was an "administrative error." The admission, however, may reopen a bitter debate between the United States and its allies over how the fight against terrorism should be conducted and compromise future cooperation. "Mistakes were made in the reporting of the information," said Gordon Johndroe, National Security Council spokesman for President George W. Bush. Johndroe insisted that cooperation between the United States and Britain would not be affected. As a sign of its misgivings about a possible reaction, the State Department sent its top lawyer, John Bellinger, to London on Thursday on a two-day mission. Bellinger will try to defuse what many expect will be widespread anger that the United States, when asked in 2004, incorrectly assured its closest ally that neither British soil nor its airspace had been used in moving suspected terrorists, officials said.