WASHINGTON – President Bush’s new chief of staff said yesterday it was time to “refresh and re-energize the team,” and he told senior White House aides who might be thinking about quitting this year to go ahead and leave now.

Taking charge in a time of crisis, with Mr. Bush’s poll ratings at their lowest point ever and Republicans anxious about the November elections, Joshua Bolten laid down his pointed directive at his first meeting with top presidential aides.

He did not ask for anyone’s resignation, and none of the senior aides stepped forward to say they would go, White House press secretary Scott McClellan reported later.But Mr.Bolten has Mr.Bush’s full authority to make changes to the president’s staff,and Mr.McClellan said he would expect announcements soon.

One of the first jobs to be filled is that of budget director – the position that Mr. Bolten left to become chief of staff. The job of domestic policy adviser at the White House is open as well. Further changes are clearly on the horizon, and Mr. Bolten gave top aides the option of leaving first.

“He wanted to make sure he had the team in place that is going to be here for a minimum of the remainder of the year,” Mr. McClellan said. “And he said if people are thinking about leaving, that now is the time to come to such a decision.”

Mr. Bolten told the staff that he was assuming his new job at a challenging time when America was engaged in a war on terrorism.With American casualties rising in Iraq, Mr. Bush faces sagging public support, Republican angst about the midterm election and struggles with a Congress that has been resistant to some of his top priorities.

“Josh talked about how this is a time to refresh and re-energize the team and for all of us to renew our commitment as we go forward,” Mr. McClellan said. Republicans outside the White House say they expect changes in Mr. Bush’s lobbying staff and perhaps in the communications office, as well as in the Cabinet.

Mr. McClellan said Mr. Bolten’s invitation was specifically for the White House staff, but that the president will “be looking to Josh for his advice and counsel” when it comes to possible changes in the broader administration. To quell speculation about Donald Rumsfeld, Mr. Bush issued a strong statement of support for the embattled Pentagon chief last Friday.

Yesterday, Mr. Bolten was on hand as Mr. Bush toured Europa Stone Distributors in Sterling, Va., to promote his tax plans with another Cabinet member who is the focus of shake-up rumors – Treasury Secretary John Snow. Mr. Bush did not say anything publicly about Snow’s future, but waved the secretary to his side during the photo op so they would be in pictures together.

Mr. Bolten already has had closed door meetings with some top presiden tial advisers and plans more, Mr. McClellan said.

“There are a number of people that have served this president for a long period of time, and so you have to balance change with continuity,” Mr. McClellan said.

Mr. Bolten also was examining the numerous meetings that consume hours of staff time at the White House. Staffers often complain that they are tied up in meetings throughout the day that keep them from doing other work.

“Any time you have a new chief of staff coming in, you can expect that there will be some changes in some of the structure and personnel and other issues,” Mr. McClellan said.

Mr. Bolten is only Mr. Bush’s second chief of staff.Andy Card left Friday after serving Mr.Bush for more than five years.

Mr. McClellan would not comment on his own future at the White House.

“I never speculate about personnel measures,” Mr. McClellan said, repeating his standard reply to questions about staff changes with a smile.