A minor regional dispute among Latin American nations over an open seat on the United Nations Security Council has become a major U.N. contest of ideologies and influence that could crucially affect upcoming debates on Afghanistan and Iran.

After an unprecedented 149 secret ballots over the past 10 weeks, neither of the two Latin contenders, Cuba or Colombia, has been able to win the two-thirds General Assembly majority necessary to take the council chair.

As a result, the council now faces two of the most volatile security issues in its 34-year history with one less than its full 15-member complement, an equally unprecedented situation Cuba has charged violates the U.N. charter and may invalidate Council actions.

In a statement Monday, the U.N. legal counsel ruled to the contrary. While "a Security Council of less than 15 members would not be legally constituted in accordance with the Charter," the ruling said, that consideration is outweighted by a council mandate to "function continuously."

But the possibility of a challenge to the ruling, as well as the chance that either Cuba or Colombia may win in the next vote scheduled for today, or in the near future, and thus affect the current council balance, put upcoming council deliberations and decisions in question.

Already, the deadlock has caused the extension of this year's General Assembly past its scheduled mid-December closure. The near-continuous balloting, on occasion as many as six times in one day, is now the sole reason for keeping the Assembly in session. Delegation tempers have become increasingly frayed. At one point before Christmas, the U.S. and Colombian delegates heatedly asked for a investigation of possible vote tampering.

The conflict is both between the Eastern and Western superpowers, each of whom want to fill the seat with a sypathetic government and among the primarily Third World nations who fill the ten nonpermanent council seats on a rotating basis.

Under normal procedure, candidates for half of the two-year, nonpermanent council seats are nominated each year by regional caucuses within the General Assembly. When the Latin American group, reflecting its own internal political differences of opinion between the pro-Western Columbian democracy and Cuba's Soviet-backed communist government, was unable to agree on a single candidate to fill the chair being vacated by Bolivia, it presented the assembly with the two contenders.

While Cuba consistently has received a pure majority in the 149 ballots to date, it has been unable to garner the required two-thirds of the assembly's 152 votes.

The United States has been Colombia's most visible backer in the contest.

Its diplomats have provided much of the manpower for intense lobbying efforts, including rounding up pro-Colombia voters each time a ballot is called for on the General Assembly floor, and monitoring the aisles to prevent what they charged was possible double-balloting by some delegations.

"We set out from the beginning that Cuba should not be in the Security Council," said one administration source. "There was no real (U.S.) debate on the issue, and it became policy during the (September crisis over Soviet troops" stationed in Cuba.

What U.S. diplomats agree began as a "relatively low-key" lobbying effort has been "stepped up in the past two weeks" in view of the Iran, and now Afghan, situations.

The reason, one U.S. official said is "obvious.On East-West issue, like Afghanistan, (Cuba) will support the Soviet Union," one of the five permanent Security Council members along with the United States, France, Britain and China.

And Cuba, the United States charges "will go against the wishes" of the 95-member nonaligned movement, even though it has pledged to represent them as movement chairman.

Cuba, which has not held a council seat during the nearly 21 years of President Fidel Castro's government, sharply disagrees. In a speech to the General Assembly last Friday, Foreign Minister Isidoro Malmieca warned of "dangerous consequences," including "a crisis of [council] prestige, authority and efficacy" if Colombia does not withdraw it candidacy in the face of Cuba's clear and consistent majority.

Such withdrawal has been U.N. practice in other regional contests when one contender had a clear plurality.

Malmierca's virtual residence in New York since the balloting began, and his presence at the assembly for nearly every vote, is one indication of the importance Cuba places on winning. Cuba first requested the seat in 1977 and has spent two years lobbying for it, both in New York and through high-level missions sent to visit African, Asian and a number of European governments.

The nonaligned movement has split on the issue, but Cuba regularly gets 85 to 95 votes, indicating a majority of nonaligned states favor Havana.

But a hardcore of at least 20 African and southern Asian nations have voted for Colombia, reflecting fears within the movement that Cuba is trying to pull nonaligned nations toward the Soviet Union.

Columbia, whose vote count to date has not exceeded 60, maintains the regional council seat should reflect regional priorities. As many as 20 of the 28 Latin U.N. members, mostly democracies or military regimes, favor its candidacy.

Cuba angrily refused an offer made by Colombia last week to split the council term, with each taking the seat for one year.Under Council practice of precedences based on alphabetical order, Colombia presumably would have the first year under such a plan.

According to the legal counsel ruling, "the balloting must continue until a result is achieved; i.e. [according to the U.N. charter] and go on until all the places have been filled."

Other current nonpermanent council members are Bangladesh, Jamaica, Portuegal, Zambia, Norway, Germany, Tunisia, Niger, and the Phillipines. p