President Carter threatened yesterday to leave four new federal judgeships in Virginia vacant if Sen. Harry F. Byrd Jr. (Ind.) refuses to change his list of 10 white male nominees for the jobs.

Carter said he would use all his influence to have the senator's list expanded to include women and minority members. The president told a breakfast meeting with reporters that he would "aggressively" support such an expansion but added that if a "balanced list" could not be formulated, "there may be no judicial appointment in Virginia."

Byrd said later he would stick by his original listing, saying that in his creation of citizens' commissions to recommend judicial candidates he "did precisely what the president asked me to do."

Although Carter and White House officials later said the president's remarks were not directed specifically at Byrd and the Virginia list, his remarks came in response to questions about Byrd and the list.

"I might say that if something of that kind cannot be resolved, then there would be no appointment in Virginia, because the way the Senate operates -- this is not my preference -- Sen. Byrd could tell the Judiciary Commission that any Senate nominee for a judgeship was unacceptable to him and the Senate Judiciary Committee would not act," the president told reporters.

Under the practice known as senatorial courtesy, senators have the power to block judicial nominations in their home state, but Carter pointed out he most start the nominating process. "Either the senator or I can in effect veto the appointment of the judge," the president said.

Byrd said yesterday he was unmoved by Carter's appeal. "I did precisely what the president in a handwritten letter asked me to do," Byrd said in a telephone interview. "I was asked to appoint citizens' commissions to recommend individuals for federal district judges based on merit.

"The two Virginia Commissions recommended highly qualified individuals. No one has questioned their qualifications. While I did not make the selections myself, I have stated to the attorney general that I will support for confirmation any two of the five recommended by each commission," Byrd said.

Byrd established two nine-member commissions, one for each of the state's two federal judicial districts. Each nine-member commission had a woman and a black member, but their nominees are all white males, a point that has angered some civil rights and minority groups in the state.

Virginia's four new judgeships were created by the 1978 Omnibus Judgeship Act that created 117 new federal district judgeships across the country.

Both Carter and Attorney General Griffin Bell have urged senators to submit nominees whose selections are based on merit and said an effort should be made to include the names should be made to include the names of qualified women and minority members.

Ironically, a White House official has said it was probably a mistake that Byrd was sent a hand-written letter urging him to set up the selection panels. The letter was supposed to have gone only to Democrats and was apparently sent to Byrd because, although he runs as an independent, he votes with the Senate Democrats on procedural matters.