A federal judge yesterday postponed the trial of former White House aide Lyn Nofziger and his lobbyist-partner Mark Bragg until Jan. 11 to avoid holiday interruptions and make it easier to pick a jury.

The trial, originally set to start Nov. 16, is expected to take six or seven weeks.

U.S. District Court Judge Thomas A. Flannery took the action at a pretrial hearing at which he rejected several defense motions but observed that the substance of one, if impressed on the jury, might win acquittal for Bragg.

Nofziger, former White House political director and a close associate of President Reagan, was indicted on six counts of violating federal conflict-of-interest laws in lobbying for the scandal-torn Wedtech Corp. and other clients within months of leaving the White House in January 1982.

Bragg, Nofziger's partner in a Washington consulting firm that they established that year, was accused of aiding and abetting Nofziger in commission of one violation: an alleged attempt to influence James E. Jenkins, then deputy counselor to the president, on Wedtech's behalf in May 1982.

Federal ethics laws prohibit former high-ranking government officials from lobbying at their old agencies for a one-year period on any "particular matter" in which the agency has "a direct and substantial interest."

Bragg's chief defense attorney, Richard Ben-Veniste, argued that the alleged attempt to influence Jenkins -- by means of a May 28, 1982, letter sent to him by Nofziger -- was an illusion.

Speaking of an interview that he said he had with Jenkins last week, Ben-Veniste said Jenkins himself dictated most of the letter, in conversations with Bragg. Ben-Veniste said that the letter was supposed to be sent to the Army, which was still resisting award of a small-engine contract to Wedtech on grounds that the price was too high but that Nofziger sent it to Jenkins instead, while Bragg was out of town.

"This was a mixup," Ben-Veniste contended. "How in the world could Mr. Bragg have intended to influence Mr. Jenkins by sending a letter that Mr. Jenkins had suggested to Mr. Bragg? . . . . You can't influence yourself. It was Mr. Jenkins' idea."

The "Dear Jim" letter, which Nofziger signed, asked for Jenkins' assistance in securing a letter of intent from the Army so Wedtech could use it in seeking additional funds from other government agencies and close "the remaining $1 million gap" between what Wedtech wanted and what the Army was willing to endorse.

Deputy independent counsel Lovida H. Coleman Jr. maintained that "there is a lot less here than meets the eye." She said that the letter was an attempt by Nofziger to obtain Jenkins' help and that Jenkins' receptivity to it was not an issue.

"Mr. Bragg seems to forget that it is his state of mind that is at issue in this case," she said.

Ben-Veniste maintained that his discoveries warranted dismissal of the charge against Bragg on grounds that the grand jury would not have indicted him had it been fully informed. But Flannery said his inspection of secret grand jury testimony showed that the basic point of Jenkins having told Bragg what should be in the letter "was brought to the attention of the grand jury."

Since Jenkins will be a trial witness, the judge said, the matter can be thrashed out then.

"I think that might constitute a good defense, if the jury believes your version," Flannery told Ben-Veniste. "You're very persuasive. If you can be just as persuasive before a jury, I think your client has a good chance of being acquitted."

At the same time, Flannery dealt the defense a blow on the question of intent. The judge held that the ethics law is "a public welfare measure" and that the burden of compliance is on the defendants.

Since they should have known the law, the judge ruled, the government does not have to prove that they knew they were violating it.