Supporters of legislation to implement the Panama Canal treaties yesterday drafted a package of amendments designed to defuse efforts to cripple the bill.

The controversial bill, which has been held off the House floor for a month because of lack of votes to pass it, will go to the floor today.Democratic leaders believe they have the votes to pass it.But they are less certain that they can hold off amendments by Rep. George Hansen (R-Idaho) that would force Panama to pay the costs of implementing the treaties. If adopted, the administration says, the amendments would force Panama to reject the canl treaties.

Hansen contends the administration lied when it said the treaties would not cost U.S. taxpayers. By lumping all costs and property values together, he comes up with a cost of $4 billion over the 20-year life of the treaties. He calls his amendments forcing Panama to pay the costs "the honesty amendments."

But administration officials dispute the cost figures, estimating the costs at from $300 million to $870 million, most of which they say is to go for moving U.S. military facilities and for taking care of U.S. military and civilian personnel in Panama.

They contend Hansen's package violates the letter of the treaties and, if adopted, would force Panama to declare the treaties void. Old treaties allowing the United States to operate the canal and to keep a defense force there would also be null and void and the canal would revert to Panama anyway and the United States would have to learn the area, the administration claims.

The package of amendments by supporters of the implementing legislation doesn't go much beyond what is already in the bill, but as one source said, "The idea is to give members something they can vote for that doesn't violate the treaties."

As outlined by Merchant Marine Committee Chairman John Murphy (D-N-Y.), the package would reiterate that no payments could be made from tax revenues unless approved by Congress and that the United States retains discretion over tax payments made for U.S. military and civilian workers and their facilities.

In addition, the package would withhold authority to transfer property to Panama until Panama paid all its debts add up to about $8.9 million owned to the present canal company. What the United States would pay to run a new U.S. Panama Canal Commission would also have to be repaid by Panama.

Meanwhile, Panama announced it has broken off relations with Nicaragua, but so far the Panamanian government has not officially recognized the Sandinista rebels as it once intended to do.

Panama's support of the Sandinistas has become an issue in the canal bill debate, but a State Department spokesman said it has been defused somewhat by reports of the Nicaraguan National Guard firing on Nicaraguans not involved in the fighting and by a growing feeling that the government of Nicaraguan President Anastasio Somoza is doomed.

State Department lobbyists are arguing that defeat of the treaty bill would badly hurt U.S. relations with Latin American countries at a very sensitive period and would erode Latin America's confidence in President Carter.

Majority leaders Jim Wright (D-Tex.) said defeat of the legislation is "not going to benefit the United States in the slightest. It will simply not allow the United States to ensure the defense and protection of its personnel and probably result in the closing of the canal."