Indonesia's longest and bloodiest conflict is in imminent danger of breaking out again, just four months after a peace agreement was signed to international acclaim.

The government last Thursday told troops to be ready to go back to war in Aceh within five days if necessary, unless disputes over the pact can be settled at a meeting of a Joint Council – the final arbiter.

Separatist rebels said they would refuse to attend any meeting inside Indonesia and proposed Geneva. Mediators from the Henry Dunant Centre were frantically trying to get agreement on a date and venue. The accord to end the 26-year war in the energy-rich province on Sumatra island looks increasingly fragile.

"We might by some miracle get through the next five days," said Sidney Jones, Indonesia project director for the International Crisis Group, on Friday. "Even if we get that far I think the mood in government and cabinet and the public at large is 'Crush separatists'. It will be very difficult to get the process back to the negotiating table."

If the Free Aceh Movement (GAM) refuses to take part in a Joint Council meeting, Jones said, "it will be a green light to the army to go ahead – the signal the army has been waiting for." Force has failed in the past.

"During the 25 years of the Aceh conflict, a military approach has always failed while a dialogue approach has not been proven to fail," media reports quoted analyst J. Kristiadi as saying.

Human rights activist Munir said a new military operation "will not produce anything but more civilian casualties." He said it was very possible conflict could be imminent.

Jones faulted both sides. During the first two months after the agreement, "GAM undertook 'in your face' rallies and went around using every possible forum to tell people this agreement was the first step to independence," she said.

The pact makes no mention of independence, which Jakarta implacably opposes. Both sides supposedly accept autonomy as a basis for further talks.

The rebels had regained control of the civilian government structure in a number of places at sub-district and village level and had been recruiting, Jones said.

The army for its part had been using its old East Timor tactics, she and other analysts said, by mobilising civilians to protest outside or attack offices of the Joint Security Committee which monitors the truce.

Monitors were withdrawn from field offices last week due to fears for their safety. Killings sharply increased, with 16 between Tuesday and Thursday.

Analysts said top security minister Susilo Bambang Yudhoyono is trying to fend off rising demands from the army and much of the public for a military operation.

"It's clear there were a lot of army objections to the idea of negotiating with the rebels – Endriartono (armed forces chief Endriartono Sutarto) and Yudhoyono persuaded the military to go along," Jones said.

One way to get GAM to stop fighting could be to offer incentives to take part in the political process, Sinn Fein-style. But the government refuses to accept locally based parties.

A start by GAM in disarming could also reduce tension. "But it's got to a point they (GAM) will say that with the army out for blood, the last thing they will do is lay down their arms," Jones said.

At some level in the army there was a genuine concern that it was being denied its rightful role to defend the integrity of Indonesia.

The army is also trying to regain the dominating role it enjoyed for decades under Suharto.

The Aceh situation, said Jones, "is a heaven-sent opportunity to prove that only the army can deal with internal security problems – even though they had a role in creating most of them." One problem, she said, is that the peace deal assumes the army and GAM actually want peace.

"Elements on both sides have an economic interest in a continuing conflict – getting a cut from public works contracts, extortion on the roads, the marijuana trade, involvement in illegal logging." Of the estimated 10,000 deaths in the war, most have been civilians.

"Civilians will get caught in the middle where they always do," Jones said. "That's the real tragedy."