Former president Ford said yesterday it would be "irresponsible" for the Senate to approve the strategic arms limitation treaty (SALT II) simply because leaders of our European allies want it, and repeated his demand for an irrevocable five-year plan to boost U.S. defenses before the treaty is approved.

In a wide-ranging breakfast-session with reporters, in which he reiterated that he is not a candidate for the presidency and predicted that President Carter would face a "real tough challenge" from Sen. Edward M. Kennedy D-Mass.), Ford strongly rejected linking SALT II with the future of the NATO alliance.

"The United States should not make its decision on the basis of the views of some leaders of NATO," Ford said, minimizing the significance of the treaty's endorsement by European leaders. "That would be irresponsible."

In an effort to bolster support for the beleaguered arms agreement with the Soviet Union, the Carter administration has invoked the threat that delaying or rejecting the treaty would damage NATO relations and jeopardize the balance of power in Europe.

Ford, rejecting this argument, said there is reason for "concern" about the military balance in Europe, but insisted that European leaders notwithstanding, the United States should not approve the treaty without first deciding to boost its own defense spending 5 percent a year, in non-inflated dollars, for the next five years.

On another foreign policy issue, Ford backed Carter's right to terminate the U.S. mutual defense treaty with Taiwan without the approval of Congress.

"My own belief is that a president can do as President Carter did," Ford said. Carter's action was ruled unconstitutional Wednesday by a federal district court judge here, and Ford said, "Obviously, it will not be a matter for the Supreme Court to decide."

The former president took issue with Republican presidential candidate John B. Connally on Middle East policy. Ford said he had reservations about Connally's proposed comprehensive settlement, saying that he feels the "step-by-step "process" is the best hope for peace and adding that he, unlike Connally, "would not at this stage want to commit U.S. forces" to guarantee new borders in the region.

As for politics, Ford again said he is not a candidate, adding that despite press speculation, "my position is exactly where it was a year or two years ago. I am not a candidate and I have no plans to be one." He said the "likelihood" is that he will remove his name from the ballot in primary states where it is entered, but that decision will be reviewed "soon."

Ford said he thinks that Kennedy's impending candidacy would present "a real tough challenge" to Carter, "at least as tough, if not tougher" than the one Ford faced from Ronald Reagan in 1976.

"Nothing is going right for the administration," Ford said, "and the economy is not going to improve between now and next summer."

"I'm not predicting who will win," he said, "but the odds are getting less and less for the president."

Ford said Republicans would have a harder job defeating Kennedy than Carter, but said that ultimately the voters probably would reject Kennedy "because they disagree with his liberal philosophy."