Israel's religious parties are trying to coerce Mr Ehud Barak's government into a more Orthodox observance of the Jewish Sabbath - but the Prime Minister, even though the future of his coalition is at stake, is refusing to budge.
The five-man United Torah Judaism party yesterday declared flatly that it will leave the coalition on Sunday if Mr Barak allows a huge shipment of parts for a power station to be transported across the country overnight tonight - a breach of the Sabbath which ultra-Orthodox rabbis consider intolerable.
More critically to the survival of Mr Barak's government, the 17-man Shas ultra-Orthodox party is also contemplating pulling out over the issue. Its departure would deprive Mr Barak of his parliamentary majority, and force him to call new elections or begin negotiations with potential new partners, including the hardline Likud - which could undermine peace efforts with the Palestinians and the Syrians.
Ironically, the threat comes as peace talks with the Palestinians finally appear to be making real progress, with Palestinian Authority President Mr Yasser Arafat stating last night that agreement had been reached on new Israeli withdrawals from occupied West Bank land.
Mr Barak's aides acknowledged last night that the "turbine crisis", as it is being called here, was "very serious" - but added that the prime minister had no intention of capitulating to ultra-Orthodox pressure.
The heavy loads are being transported on the Sabbath because Israel's roads are relatively empty then, and the disruption caused is minimal.
Some of Mr Barak's colleagues believe that Mr Aryeh Deri, the former Shas leader who is now appealing a conviction for bribe-taking, may be helping to foment the crisis in an effort to undermine the politicians who have succeeded him in the party's hierarchy.