JERUSALEM — Back from New York with no breakthrough in the peace proces, Prime Minister Ehud Barak faces a growing outdoor happening southeast of Tel Aviv.

Outside Ma'asiyahu Prison in Ramla where Aryeh Deri, the former leader of the predominantly Sephardi Shas Party, began serving his term earlier this month, hundreds of fervently religious Deri supporters have set up camp in an empty lot near the jail.

Each night, they are joined by thousands — sometimes more than 10,000 — sympathizers from around the country who come to pray, sing and demonstrate their demand that Deri be freed.

The fallen Shas leader and longtime senior Cabinet minister was sentenced last year to a reduced three-year term in prison for accepting bribes and misappropriating state funds.

"I have full confidence in the mayor of Ramla…the Ramla police," Barak said Tuesday. "They will ensure that the law is observed."

While Barak brims with confidence, nocturnal selichot services — special pre-Rosh Hashanah prayers — last until the wee hours, relayed over a powerful address system so that those within the prison walls can join in the refrains with those outside.

Booths have also sprung up to sell items of spiritual sustenance. These — like the tents and makeshift synagogues that have been erected — are illegal structures, as is the camp itself, for which no license has been obtained.

For the moment the general feeling in government circles is that ordering in the police would trigger a violent confrontation.

But "Yeshivat Sha'agat Aryeh," or "The Lion's Roar Yeshiva," as the activists have named their encampment, could be much more than just a law-and-order problem for the government and the entire political establishment.

Remarkably, many of the demonstrators flocking here are not Shas supporters, nor even Sephardim.

Rather, they are Ashkenazi haredim, most of them Chassidim. They seem to regard Deri's cause as an all-haredi cause, worthy of their active involvement.

Some obser-vers have suggested that the incarcerated Deri is becoming a haredi leader on the national level, transcending the traditional Sephardi-Ashkenazi divide.

Of course it is still early. The test of this new mass movement's resilience will come after Yom Kippur and before the family festival of Sukkot nears. Or when the cooler, wetter nights approach.

While the longer-term scenario is still uncertain, there can be no doubt that Barak's recently announced agenda aimed at secular voters has had the side effect of drawing in the Ramla crowds firing up the rabbis and Orthodox politicians who address the faithful outside the prison walls.

Barak is proposing a series of radical changes in the decades-long "status quo" arrangements governing state and religion in Israel.

His agenda includes civil marriages, at least for those whom the Orthodox establishment refuses to marry religiously. He wants busses to run on Shabbat, as well as El Al flights — like every other international airline. He wants fervently religious schools, which are funded mainly by the state, to teach secular courses.

For the haredim, this catalogue amounts to a declaration of war on Orthodox Judaism as the established state religion.

In order to implement his new agenda, the premier would have to set up an all-secular government that excludes the National Religious Party, Shas and United Torah Judaism.

Granted, many political pundits see the whole exercise as designed to prepare an election platform rather than a realistic program of legislation in the present Knesset.

But for the moment, it is fueling an unprecedented mass protest movement that could make its own impact on party alignments in the present Knesset — and on the outcome of the next election.