BUENOS AIRES, OCT. 26 -- The retired colonel who inspired three military revolts against Argentina's democratic government has been arrested and ordered detained for two months for issuing public warnings about "extremely dangerous" unrest within the armed forces.

The arrest of former colonel Mohamed Ali Seineldin, coming at a time when President Carlos Menem is visiting Europe, has once again focused attention on an issue that refuses to go away: the still-delicate balance of power between the government and the military seven years after Argentina's return to civilian rule.

Seineldin's offense was to deliver a letter to Menem's official residence last Saturday warning that "the morale of the rank and file is such that the situation lends itself to incidents of incalculable seriousness."

Seineldin led an army uprising against then-president Raul Alfonsin at the Villa Martelli army base just outside the capital in December 1988. He was also seen as the driving force behind two prior uprisings led by one of his more charismatic followers, Lt. Col. Aldo Rico. Both Seineldin and Rico have since been forced into retirement.

In his letter, Seineldin complained bitterly that a deal he struck with the Alfonsin government to end the Villa Martelli mutiny has not been respected. "Almost two years have gone by . . . and nothing that was promised has been fulfilled," he wrote. The government has always denied the existence of any agreement.

In recent months, Seineldin and Rico have conducted an increasingly public campaign seeking popular support for their right-wing, almost mystical views about the Argentine "fatherland." They have particularly sought backing among the working class, which has been buffeted by Menem's belt-tightening economic policies. While there is no indication that Seineldin and Rico have drawn a widespread following, graffiti and posters with slogans such as "Seineldin means food" and "Seineldin means work" have become common.

When Seineldin delivered his letter, Menem had already left the country. Vice President Eduardo Duhalde immediately ordered that Seineldin be brought in for violating the military code that forbids criticism of higher-ranking officials.

Duhalde said he believed the letter was "part of a plan" to destabilize the government, but he added that he was confident that the plan would fail. Seineldin has been ordered to spend his 60 days' detention at the 4th Army Corps headquarters in Santa Rosa.