With a governor, 12 mayors, two congressmen and a small multitude of businessmen looking on, Braniff International announced in Dallas yesterday that it wants to join British Airways and Air France to provide Concorde air travel between Dallas and Europe with a stop in Washington.

The business agreements have been signed, Braniff board chairman harding L. Lawrence announced. U.S. government approval, he said, "hopefully will be in time for the peak summer season."

The Braniff announcement means that, for the first time, an American airline is interested in using the Concorde. But that positive sign for the plane's British and French builders comes at a time when Concorde is n serious difficulty, largely because it still is shut out from New York City - the one market they say they must have to succeed.

That difficulty is beginning to resemble a high-stakes poker game between Air France and British Airways on the one hand and the New York Port Authority on the other. The port authority operates John F. Kennedy International Airport in New York and must grant approval before Concorde can land there.

The New York blockade has also become a serious diplomatic issue. French President Valery Giscard D'Estaing brought it up with Vice President Walter Mondale when Mondale was in Paris. "President Giscard make it clear that they (the French) strongly hoped approval for the landing in New York would be granted," Mondale said.

And British Prime Minister James Callaghan said Wednesday that "the British and French ambassadors have now been instructed to approach the United States government to make known our concern at the further delay" in the New York matter.

Although Concorde is not officially a part of the discussion, it is certainly in the background of current U.S., British negotiations over the treaty that defines the rights of each country's airlines to land or stop over in the other country. That treaty expires in June.

British Aircraft Corp., the British builder of Concorde, has begun negotiations with labor unions to lay off 1,560 workers. They will lose their jobs if the Concorde production line does not get more orders. Five nearly completed Concordes are unsold.

The Braniff announcement yesterday will be not change that figure because Braniff's Lawrence has said he is not interested in buying Concordes, only leasing them.

Under the joint agreement he signed with British Airways and Air France, the Concordes that come to Washington's Dulles International Airport six times a week will simply fly on to Dallas - but with Braniff crews. They will return from Dallas to Washington - again with Braniff crews - where they once again will turn into British Airways and Air France flights to go back to London or Paris.

Concorde will fly subsonically - below the speed of sound - on the Washington-Dallas leg because supersonic flight creates an illegal overland sonic boom.

Lawrence said yesterday that passengers would save 18 minutes over a regular Washington-Dallas flight on conventional jets.On the leg to Europe, Concorde cuts the normal eight-hour flight to four hours. The Dallas-Washington flight, Lawrence said, would cost 10 per cent more than regular first-class fare. The 20 per cent surcharge on the transatlantic leg would remain.

The total cost of the Dallas-to-London trip on the Concorde would be $896 compared to a normal first-class fare of $745. Dallas to Paris would cost $922 compared to $771. For those who want to save 18 minutes between Dallas and Washington, they can do so for $188 vs, the normal first-class fare of $171.

Such a one-stop flight will require at least two and perhaps three specific governmental approvals. First, the Civil Aeronautics Board must approve the plan and the fares, which were filed with the CAB late yesterday."We don't know how long it will take to decide," CAB spokesman Ted Lopatkiewicz said yesterda "There's no precedent."

Because the Concorde will be flown by U.S. crews, it must be certified as "airworthy" by the Federal Aviation Administration. The FAA had once started such a procedure years ago when it looked like Pan AM and TWA might buy the Concorde, but that work is dormant and would have to be started again.

Dick Stafford, an FAA spokesman, referred all queries to the parent Department of Transportation yesterday.

DOT chief spokesman David Jewell, when asked if the FAA would begin anew the certification procedure for Concorde, said, "The FAA isn't going to do anything until we find out what the CAB does."

Furthermore, the approval Concorde has to fly to the U.S. is very limited. Former Transportation Secretary William T. Coleman Jr. said it could fly on a test basis to New York and Washington up to a maximum of one round trip per day by each airline to Washington and two round trips to New York.

Additional commercial flights would require a new decision-making process, including a time-consuming Environmental Impact Statement (EIS), he said.

Braniff's Lawrence said yesterday that, when the new Dallas airport was planned, an EIS anticipating supersonic flight was prepared and approved. thus, he concluded, a new EIS would not be needed.

Furthermore, he said, since Air France and British Airways are landing at Dulles only six times a week instead of the Coleman-authorized 14, there is plenty of room for the extra six landings that the requested Dallas service would entail.

Asked if changes would have to be made in the Coleman decision by new Transportation Secretary Brock Adams, Jewell said, "I don't know."

The Concorde is successful as far as it goes. British Airways and Air France both report they are selling more than enough seats to make the plane pay for itself on an operational basis. The problem is, the plane is unused much of the day and thus not producing revenue. A Dallas approval would help that.

New York remains the key. Air France and British Airways are pouring thousands of dollars into advertising and other campaigns to create pressure for approval by the port authority. Labor and business leaders have called press confereces in New York to announce that Concorde's Washington service is costing New York jobs and money.

Indeed, one out of every four Concorde passengers through Washington is eventually going to or coming from New York.

But the port authority board twice delayed making a final decision. And twice, attorneys for British Airways and Air France have agreed to delay pressing their lawsuit against the port authority seeking access to Kennedy. A hearing on the suit is scheduled in federal court in New York for next Friday.A decision on whether to proceed will probably go down to the 11th hour, according to Concorde sources.

But in Dallas yesterday, all was rosy. Texas Gov. Dolph Briscoe, the mayors of Dallas, Fort Worth and 10 surrounding communities and local business leaders praised Braniff's initiative. Said Briscoe: "This step is equal to any other taken in the history of transportation in this state . . . "