James Miller, resigning as the White House budget director, will be replaced by deputy Joseph Wright, who will write the budget for fiscal 1989 in the waning days of the Reagan administration.

President Reagan called Miller "an old comrade in arms" and praised his service Wednesday during a ceremony attended by employees in the Office of Management and Budget. Miller's resignation is effective Oct. 15."It goes without saying that I am sorry to see Jim go," Reagan said. "He's made an outstanding contribution to our administration and our nation these last few years."

A White House spokesman said the OMB director's position requires Senate confirmation but Wright would be appointed acting director and "no decision has been made on a nomination."

Miller, who has been at the budget office in several positions since Reagan's presidency began, will take a position at George Mason University in Virginia, the president said.

"In each post he served with distinction," Reagan said of Miller.

Reagan said Miller, in his first stint at OMB and while head of the Federal Trade Commission, "played a leading role in removing the shackles of excessive regulation from our economy. And I believe that a great deal of the credit for our recovery goes to that effort."

Miller compared his tenure to the time he received his doctorate of philosophy, when his mother told him no one could ever take that away from him.

"I feel that about my experience working for you," Miller said. "Thank you, Mr. President."

He also assured Reagan a "transition will be as smooth as a muddy lake," saying, "You won't miss me, Mr. President. It will be so smooth."

Wright pledged to work toward reducing the federal deficit and said, "Don't worry about it, Mr. President. It will come down."

And turning with a word to his colleague, Wright said, "Jim, I've been riding shotgun for you for two years . . . and I'll move on over and guide the horses straight."

Reagan used the ceremony to exhort Congress to complete work on a handful of outstanding appropriations bills before the new fiscal year begins Saturday.

Miller will become a distinguished fellow at the Center for Public Choice at George Mason University, and also will hold the same position for Citizens for a Sound Economy and chairman of an advisory board for Washington Economic Research Consultants.

"It will be hard to fill Jim's shoes," Reagan said, "but if there is a man to do it, it's Joe Wright. He's been here from the very first day."