House-Senate conferees reached a quick new compromise yesterday on legislation to implement the Panama Canal treaties, which take effect Oct. 1.

The bill is slated for swift Senate and House action, and supporters believe it has an excellent chance.

In the wake of last Thursday's House floor defeat of the first conference compromise, House opponents obtained new concessions.

These include language -- in the report accompanying the bill -- that would permit the president to place the canal under military control in case of a threat to the security of the canal. Any circumstances in which foreign troops were located in Panama would be considered a threat.

Asked if President Carter would go along with the conference agreement, an administration official siad, "We don't have a whole lot of choices at this point." But he added that the administration was successful in keeping out anything that would directly violate the treaties.

House Merchant Marine Committee Chairman John Murphy (D-N.Y.), predicting passage, said, "I've spoken to more than enough members of Congress and they said they would change their vote," Murphy said last week's defeat was due partially to the absence of members last Thursday for the Jewish holidays.

In addition, Rep. Robert Bauman (R-Md.), a leading opponent, signed yesterday's agreement and said he would support it on the floor though he would not vote for it. He had refused to sign the earlier report.

"I think I can go back and honestly say the House has the best deal it can get. We have an obligation to honor the treaty," Bauman said. "Many concerns expressed last week have been met."

It was Bauman who insisted on report language allowing the president to place the canal under military control if foreign combat troops are placed in Panama. Bauman and others have been concerned about Panama's friendship with Cuba, and Bauman said the language would protect the United States if a Cuban or Soviet brigade were brought into Panama.

But the language does not make it mandatory for the president to act, and Bauman admitted it was intended as a "message to the president" of Congress's desire.

The treaties turning the canal over to Panama were ratified by the Senate in 1978. They go into effect Oct. 1, whether or not Congress passes the implementing legislation. Without the legislation's new mechanism, Murphy said, "There is no payroll, no company, no structure in force to operate the canal," as the United States has agreed to do until it finally turns the canal completely over to Panama in 1999.

As part of the conference agreement reached yesterday, the conferees re-emphasized that the canal itself would not be transferred before the 1999 date.

About 55 percent of the property will be transferred to Panama on Oct. 1. The conferees agreed that any future transfers will be subject to congressional approval, and that the president will have to give Congress 180 days' notice of any future transfers he intends. The agreement does not specify what action Congress might take if it disapproves of the transfer, leaving it impled that Congress might take action. In fact, however, a disapproval by Congress of its commitment to transfer property in the future would be in violation of the treaties.

The conferees also agreed that:

Slightly more of the costs of implementing the treaties will have to come out of tolls;

Certain housing and health care costs of U.S. workers would be deducted from the tolls before Panama could receive any payments if the tolls exceed operating and maintenance costs;

Three of the five U.S. members of the commission set up to operate the canal would have to represent shipping companies, port authorities and labor.

Carter last week told House members that the rejection of the first conference report was "the most disappointing" legislative defeat he had suffered all year. Strong right-wing lobbying, with letters pouring into members' offices, was credited with forcing 78 Democrats to vote against the legislation.