Mount Kisco, N.Y. — Former Secretary of State Cyrus R. Vance says that the Reagan administration is confronting foreign challenges without coherent long-range plans.
In a rare interview, Mr. Vance asserted that in dealing with the Soviet Union and the Middle East, the administration appears to lack clear-cut plans and positive objectives. As a result, he said, the danger of conflict between the United States and the Soviet Union and between Israel and its Arab neighbors has increased.
When it comes to dealing with El Salvador, Vance said he believes that the administration has failed sufficiently to address the underlying economic and political causes of tension and has placed too much emphasis on military assistance.
On the positive side, Vance welcomed President Reagan's recently announced Caribbean Basin initiative. He said that it may be a case of too little too late , but that it is a step in the right direction. He said he now believes that the administration should go a step farther, and embrace Mexico's recently formulated peace proposals. The US should let Mexico take the lead in finding a solution to the crisis in Central America, he said.
Also on the positive side of Vance's assessment of the Reagan administration's first year in office is Poland. The former secretary of state contended that the administration has, for the most part, dealt correctly with the crisis in Poland.
Despite tensions between the United States and the Soviet Union over Poland and other issues, Vance said he thinks that the US may now be facing opportunities for major progress in arms control negotiations with the Soviets. That progress could come, he said, in agreements on limiting both nuclear and nonnuclear weapons.
After resigning as secretary of state in April 1980, Vance continued to take an interest in arms control. He resigned because he was unable to support President Carter's decision to launch the ill-fated helicopter mission to rescue the American hostages being held in Iran. Vance returned to his law practice in New York, where he has been specializing in international law.
In September 1980, Vance joined the Independent Commission on Disarmament and Security Issues, an 18-member, nongovernmental international commission that is preparing, among other things, proposals for the 1982 United Nations special session on disarmament. The commission recently held its 10th meeting at Mount Kisco, N.Y.
Appearing much more rested and relaxed than he had been during his last days in office, Vance spoke with some optimism about the possibilities for arms control. He said that both the Soviets and the Americans were adhering to the spirit of the SALT II treaty that he had helped to negotiate. He said that he had the impression that the Soviets might now be prepared to accept the modifications to that treaty which the US Senate Foreign Relations Committee recommended in 1979.
Vance also said that he was convinced that the Soviets would be prepared to make further cuts in the ceilings and subceiling which were set by the two sides for strategic nuclear missile launchers.
On the subject of controlling nonnuclear, or conventional, weapons, Vance said there are signs that the prospects for agreement between the Americans and Soviets are brighter than most people realize.
''I think the Soviets would be prepared to negotiate seriously the parity of all forces within Europe, and I define Europe as going back to East of the Urals ,'' said the soft-spoken former secretary of state. ''I think it's possible to get around the data base problem. . . . I think there's more flexibility there.''
Vance said that he sees a trend toward a commendable pragmatism developing within the Reagan administration when it comes to dealing with a number of issues, including US-Soviet arms control. But he also sees a danger that pressures will build on both sides to deploy new weapons systems unless a modified SALT two is accepted.
The former secretary of state said he thinks that thus far, despite the trend toward pragmatism, the Reagan administration has taken too simplistic a view of the Soviet Union, a view which does not permit rewards for positive behavior. He is convinced that belligerent rhetoric directed at the Soviets by the administration and slowness in getting arms control talks started were factors that helped to fuel the antinuclear movement in Western Europe. That movement has complicated American efforts to deploy new nuclear missiles in Europe.
''The administration doesn't seem to have recognized that for dealing with the Soviets, you have to have a plan,'' said Vance. ''If they have a plan, it's certainly not been articulated.''
''I don't think they recognize that any strategy for managing the relationship with the Soviets must have both carrots and sticks,'' he continued. ''It cannot have only sticks.''
Vance said that he could not argue with President Reagan's Nov. 18 proposal for deep cuts in European-based nuclear weapons. But he said that the proposal was much too late in coming.
Speaking of the Middle East, Vance asserted that the administration had wasted time trying to form a ''strategic consensus'' among countries in the region and had neglected to address the Palestinian issue with the seriousness it deserves. He contended that the administration's Middle East policy had so far amounted to improvising, or as he put it, ''ad hoc-ing it on a day-to-day, week-to-week basis.'' Southern Lebanon, he said, had developed into ''the most dangerous place in the world.''
''There isn't any coherent plan to move toward clear-cut objectives,'' said Vance.