The White House on Saturday defended chief of staff John Sununu against new allegations that he took personal trips at taxpayer expense and let corporate sponsors pay for his ski vacations.

As a result of the brouhaha over Sununu's trips, President Bush's legal staff prepared to tighten rules on his use of government aircraft.The policy review by White House counsel Boyden Gray will likely urge Bush to establish a process in which Sununu would have to get a sign-off on whether his trips are considered official, personal or political, a senior administration official said Saturday.

Currently Sununu makes the determination whether he or a political party should reimburse the government.

Gray's review will likely recommend that Sununu follow the same guidelines as Bush and Vice President Dan Quayle when they mix political travel with official business, said the official, who spoke on condition of anonymity.

In those cases, the Republican Party or a specific candidate's campaign fund must reimburse the government when Bush and Quayle and their aides travel on Air Force planes for political business.

Bush ordered Gray to look at the policy rather than investigate Sununu's travel, the senior official said. But if it becomes apparent that Sununu charged political trips to the government, reimbursements will be ordered, the source said.

Bush insisted Sununu had complied with the rules but hinted he might want them changed to avoid the appearance of impropriety.