Argentines talk tough on still-hot Falklands issue

''Ronald Reagan is now trying to atone for his treachery earlier this year when he supported Britain in the war over the Malvinas.''

Those are the words of a well-placed Argentine Army colonel, commenting on recent United States support for United Nations and Organization of American States resolutions calling on Argentina and Britain to resume negotiations in their dispute over the Falkland (or Malvinas) Islands.

Like many Argentines who remain angry over the US decision last April to side with Britain in the dispute, the colonel, a member of the Army general staff, was visibly bitter.

''It will take more than voting for a UN resolution if the US is to undo its treachery in supporting the British,'' he said.

Thumping the desk angrily, he added:

''No righteous nation would have done what the United States did. The world knows that. And anyway, we have the support of all good people everywhere in demanding that Britain give up the islands.

''And if it doesn't do that, we will invade them again and take them over, wiping out the British aggressors.''

There can be no mistaking the Argentine determination eventually to wrest control of the Falklands. Argentina has begun acquiring new weaponry. But it will take time and money, at least $5 billion, just to restore Argentine forces to their prewar strength. To beef them up more, as the military plans, will prove a heavy burden to the Argentine economy.

Already, 12 French Etendard jets and an unknown number of Exocet missiles, contracted and largely paid for before the war, have been delivered. ''This is only the start of our rebuilding,'' the Argentine colonel said. ''We need and will get whole new weapons systems, the most modern in the world, so we can dislodge the British from the islands.''

''They are our islands,'' President Reynaldo Bignone says.

Store windows, bumper stickers on automobiles, and billboards express similar sentiments. Street demonstrations in favor of eventual Argentine control of the islands occur regularly. And radio announcers sometimes end news broadcasts with a reminder that Britain controls the Falklands ''illegally and immorally,'' as one put it.

The bitterness is obvious, although the sharp edges of anti-British feeling so evident in April, May, and June during the war are dissipating. The London Tailors, which took ''London'' out of its name in May, is putting it back. The London Grill, which suffered a falloff in customers during the fighting, is enjoying a modest upsurge in business as its traditional clientel returns.

But the anger at the US, felt particularly in military circles, is something else. During the war, Britain was the honorable enemy, the US the dishonorable friend.

''The United States broke every moral code in supporting Britain,'' a Navy admiral comments. ''It ended forever its claim to any voice in inter-American affairs.''

Argentines remain convinced they have the support of their sister nations in the hemisphere - despite considerable evidence to the contrary and despite the recent warnings on human-rights issues given by Venezuela, the nation that was strongest in its backing of Argentina during the war.

There are, however, a few warning voices. J. Iglesias Rouco, the respected front-page columnist for the morning La Prensa, wrote recently that Argentina's whole South Atlantic policy was ''shipwrecked.'' He called on Argentina to rethink the question.

Some Foreign Ministry officials wonder if it might not be best for Argentina to sideline its claims to the Falklands and get on with the business of ''straightening out the hopelessness of our economy.''

One radio commentator asked if, in the long run, the solution of ''our economic and political malaise would be helped or hurt by continuing to insist on sovereignty over the Malvinas. And I have to suggest that if we dropped the issue from public attention, we might have more energy to focus on issues that are more important.''

While such views are beginning to emerge, they are at best tentative. They also are almost lost in the flow of continuing demands that Argentina press its case on the Falklands.

Moreover, with the military continuing to dominate politics here, the issue is likely to remain in public view for the foreseeable future. Then, too, the charges and countercharges over responsibility for the defeat echoing through the corridors of the military high command are certain to keep the issue on the front burner.