President Carter told the American people last night that the Senate should approve the Panama Canal treaties because that is "what is right for us and fair to others."

Quoting Theodore Roosevelt, under whom the initial canal agreement with Panama was negotiated, the president said the new treaties not only will protect U.S. interests but will demonstrate "the kind of great power we wish to be."

Carter's nationally televised speech from the White House came at a time of increasing signs that both public opinion and the sentiment of the Senate are flowing toward approval of the treaties, which were signed last September.

A Gallup poll released yesterday showed 45 percent of the public in favor of the treaties and 42 percent opposed, a significant shift from three months ago, when a similar poll showed 48 percent against the treaties.

Moreover, two more senators - John A. Durkin (D-N.H.) and Patrick J. Leany (D-Vt.) - yesterday announced that they will vote for the treaties, raising to more than 60 the number of senators believed ready to support the administration on the issue.

The votes of 67 senators - two thirds of the full Senate - are necessary for approval.

The White House has been seeking to sway public opinion on the canal issue for months, inviting dozens of groups to Washington for briefings on the treaties and dispatching numerous spokesmen around the country to virtually any group willing to listen.

Last night's talk from the library of the White House, in a relaxed "fireside chat" atmosphere, was the president's most direct personal appeal to the public on the issue.

Although such a talk had been in the planning stages for months, and presidential aides had known for a week that it would be given this week, the talk apparently went through some hurried last-minute changes. A text of Carter's remarks was promised for 5 p.m. yesterday, but was not delivered to reporters until almost three hours later.

In the meantime, top Carter aides - including press secretary Jody Powell, political adviser Hamilton Jordan and pollster Patrick Caddell - huddled in Powell's office apparently reworking the speech.

The treaties, approval of which is one of the administration's top priorities for this year, would turn over control of the canal in stages to Panama, with Panama assuming complete control by the year 2000. The treaties also give the United States the right to defend the canal indefinitely and grant to U.S. and Panamanian warships a guarantee of "expeditions passage" through the canal.

A separate agreement between Carter and Panamanian leader Gen. Omar Torrijos spells out U.S. defense rights more explicitly and has been incorporated into the treaties by committee amendment in the Senate.

In his talk last night, the President made no new pronouncements about the treaties, nor did he raise new arguments in favor of their approval. Instead, he sought to answer what he called the "most common questions" about the treaties and to appeal to Americans' sense of "good will and fairness."

Declaring that the United states has the right to be proud of the canal, Carter said:

"Still, we Americans want a more humane and stable world. We believe in good will and fairness, as well as strength. This agreement with Panama is something we want because we know it is right. This is not merely the surest way to protect and save the canal. It is the strong , positive act of a people who are still confident, still creative, still great."