His voice dripping with sarcasm, White House press secretary Jody Powell yesterday described the latest suggestion of differences between Secretary of State Cyrus R. Vance and national security adviser Zbigniew Brzezinski as an example of "damn-the-facts, full-speed-ahead journalism."

The White House has always been especially sensitive on this issue, taking pains to deny any rifts. The new report "illustrates the point," Powell said, "that once some folks make up their minds how they're going to report something, it doesn't make any difference on God's earth what you do".

Powell, who said he was reflecting President Carter's attitude, was offended by reports yesterday by The New York Times and Reuter news service on speeches Vance and Brzezinski gave Monday to a conference of businessmen on U.S. policy toward China. The Times reported that the speeches appeared to reflect "different perspectives," with Vance emphasizing the need for an "evenhanded" approach to China and the Soviet Union, and Brzezinski stressing the strategic advantages to the United States in its new ties to Peking.

From the beginning of the Carter administration, there have been recurrent suggestions and reports of differences between Vance, the cautious Wall Street lawyer turned diplomat, and Brzezinski, the Polishborn academic who is considered the more "hawkish" of the two. The White House has consistently denied the existence of differences. Yesterday, Powell chose sarcasm as his method to take issue with the latest such reports.

Saying that Vance and Brzezinski had decided to do "a daring thing" by giving speeches on the same topic the same day, Powell said it occurred to some in the White House that "there might be an inclination to interpet the speeches as conflicting no matter what wa said."

To guard against that, he continued, the two speeches were "carefully coordinated."

"They personally collaborated in drafting the speeches -- Secretary Vance reviewed Dr. Brzezinski's speech, and Dr. Brzezinski reviewed Secretary Vance's speech," Powell said. "They even called each other to check on last-minute changes. And just to make sure, the president read both of the speeches.

"It seemed to the president, to Secretary Vance and to Dr. Brzezinski that they were all in agreement. But with the casual arrogance that sometimes rears its head, the fact that all of them thought they were in agreement did not deter the insightful analysis we saw today."

Powell added, in a tone of lightheadred resignation, that neither he nor the president was "really upset" that all these efforts came to naught. "It's so damn ridiculous it's mindboggling," he said.

Asked if there were any disagreements at all between Vance and Brzezinski, Powell said, "I don't know about that." But he said it was safe to assume that on the China speeches, each man agreed with what the other said.

The reaction at the Sate Department was more restrained and less sarcastic but no less critical of suggestions about differences over China policy.

"The secretary, and I am speaking on his behalf, categorically rejects the notion that what the two said yesterday was in conflict or reflects differing assessments about the world generally, about our relations with China or about the Soviet Union," said department spokesman Hodding Carter."

"The perception of conflict is in the eye of the beholder," he added.