By Nick Miles Central America correspondent

The Nicaraguan congress reconvenes after its summer recess facing perhaps its most important decision in recent years.

Within a few weeks, possibly days, congress has to decide whether to lift former president Arnoldo Aleman's immunity from prosecution so he can stand trial on corruption charges.

Public prosecutors say he embezzled almost $100m dollars during his time in office.

Parliament is coming under pressure to act from President Bolanos

The United States has taken a keen interest in the scandal and governments across the region will be watching developments closely, in what could prove a test case for corruption issues across the region.

The case has galvanised public opinion from all sectors of Nicaraguan society against Mr Aleman - from the left-wing former Sandinista president Daniel Ortega to Nicaragua's business community.

Half a million people have already signed a petition urging the congress to withdraw the immunity from prosecution that Mr Aleman enjoys as head of the Nicaraguan national assembly.

'Massive looting'

Nicaragua's attorney-general has accused Mr Aleman and 13 associates of looting almost $100m of public funds before he left office earlier this year.

That's equivalent to the government budget for a whole year.

The government claims that Mr Aleman laundered the funds through front companies and bank accounts in Panama, and the Caribbean - Mr Aleman has denied any wrongdoing.

But Enrique Bolanos, who took over from Mr Aleman as Nicaragua's new president in January, seems determined to push ahead with the case.

Most Nicaraguans live in poverty

The two men are both from the Liberal party and are long-time friends. But Mr Bolanos made tackling corruption a key issue in his election campaign, and he seems to be living up to that promise.

Lifting Mr Aleman's immunity from prosecution requires only a simple majority vote.

But he still has the support of his party, which holds the majority of the 92 seats.

Even if his supporters vote with him his troubles may not be over.

President Bolanos is threatening to organise a national demonstration against the assembly if it does not agree that Mr Aleman should be tried.