Despite reports of new flexibility on the part of Argentina, the question of sovereignty is still blocking a resolution of the Falklands crisis, according to United Nations officials.
A UN official stresses, however, that diplomatic probing continues. Secretary General Javier Perez de Cuellar hopes to find a formula that would permit a disengagement of military forces and the start of British-Argentine negotiations on the Falklands' future, he says.
The problem, the official says, is that while Argentina is not insisting on Argentine sovereignty over the islands as a precondition for direct negotiations , the question of sovereignty has ''reappeared in another guise.'' Argentina is saying that once direct negotiations begin, they should be fashioned to lead to Argentine sovereignty.
What the UN secretary-general is trying to do is separate the military forces of the two sides and get negotiations started without focusing on the nettlesome question of sovereignty.
''It's recognized by everyone that you can't return to the status quo ante and that Argentina would eventually get sovereignty,'' says a UN official. ''But we can't put that down on paper.''
In Washington, US Secretary of State Alexander M. Haig Jr. said May 10 that he saw some ''positive elements'' in recent Argentine statements. Other State Department officials caution that a measure of skepticism was required when it came to signs of diplomatic progress.
''The Argentines could be stalling,'' a State Department official says.
If nothing else, the hints of greater flexibility serve as a useful public relations ploy for Argentina at a time when Britain appears to be contemplating landing on the Falklands. If that occurs, the Argentines can accuse Britain of showing bad faith in the midst of negotiations.