An ultra-Orthodox minister in Israeli Prime Minister Benjamin Netanyahu's coalition government was expected to quit on Sunday in a dispute over work on the Sabbath, the Jewish day of rest.
But Health Minister Yaakov Litzman's United Torah Judaism party was expected to stay in the ruling alliance, preserving Netanyahu's slim parliamentary majority.
The dispute is over essential railway maintenance work, which is far less disruptive to commuters on the Sabbath, when no trains run.
Sabbath begins at sundown on Friday and ends at sundown on Saturday.
"Health Minister Yaakov Litzman informed Prime Minister Benjamin Netanyahu that it is his intention to resign from the cabinet on Sunday if any kind of work is carried out on the Sabbath," his spokesman said in a statement on Friday.
Such work was carried out on Saturday, media said.
Netanyahu was reportedly seeking to persuade Litzman not to resign by offering backing for various measures the health minister and his supporters favour.
Ultra-Orthodox parties have often played a kingmaker role in Israel's politics.
They control 13 seats in Netanyahu's coalition, which has 66 out of 120 seats in parliament.
They demand strict adherence to Jewish law, particularly on the Sabbath, when no work is allowed.
Electricity must not be turned on or off and engines must not be operated between sunset on Friday and sunset Saturday.