Israeli Prime Minister Benjamin Netanyahu has vowed to press ahead with his contentious judicial overhaul, despite unprecedented mass protests at home, growing defections by military reservists and appeals from the US president to put the plan on hold.

Netanyahu’s message, delivered in a prime-time address on national television on Thursday, set the stage for stepped-up street protests in the coming days leading up to a fateful vote expected on Monday.

Thousands of people marched through central Tel Aviv on Thursday night, while others continued a roughly 70-kilometre march from Tel Aviv to Jerusalem.

Netanyahu was at times conciliatory during his address, saying he understands the differences of opinion that have bitterly divided the country and offering to seek a compromise with his political opponents.

He said Israel "would continue to be a democracy", and said statements by hundreds of reservists that they would refuse voluntary service if the overhaul passes were harmful to the country.

"What will endanger democracy is refusal to serve in the military," Netanyahu said.

"We cannot tolerate that and we won't tolerate that."

Parliament is expected to vote Monday on a bill that would curtail the Supreme Court's oversight powers by limiting its ability to strike down decisions it deems "unreasonable."

The reasonability standard is meant as a safeguard to protect against corruption and improper appointments of unqualified people.

The bill is one of several keystone pieces of the Netanyahu government’s judicial overhaul plan.

Netanyahu and his allies — a collection of extremists and ultra-Orthodox parties — say the plan is needed to curb what they consider excessive powers of unelected judges.

Critics say the legislation will concentrate power in the hands of Netanyahu and his far-right allies and undermine the country’s system of checks and balances.

They also say Netanyahu, who is on trial for corruption charges, has a conflict of interest.

'War of attrition'

The proposal has bitterly divided the Israeli public and attracted appeals from US President Joe Biden for Netanyahu to slow down and forge a broad national consensus before passing any legislation.

After Netanyahu's speech, opposition leader Yair Lapid urged Netanyahu to defy his coalition allies and halt the legislation.

"This extremist group has no mandate to turn Israel into a messianic and non-democratic state," Lapid said.

"The Netanyahu government is waging a war of attrition against the citizens of Israel."

Perhaps the biggest threat to the plan is growing calls by military reservists who say they will stop reporting for duty in key units.

They include fighter pilots, commandos and cyberwar officers. Israeli leaders and military commanders have expressed growing alarm, saying the refusals to serve could hurt the country’s security.

Reservists, whose service is voluntary, make up the backbone of Israel’s military.

On Thursday, the former head of Israel’s Shin Bet internal security agency, Nadav Argaman, voiced support for the reservists.

"We need to stop this legislation by any means," he told the Army Radio station, saying the reservists "are very concerned and fearful for the security of the state of Israel."

Massive protests

Tens of thousands of Israelis have joined mass protests against the overhaul since it was proposed in January, and business leaders have said that a weaker judiciary will drive international investors away.

The movement has also begun to shift its focus from Tel Aviv, where weekly demonstrations draw tens of thousands, to Jerusalem, where the parliament is set to vote next week.

Hundreds of protesters packed up rows of small white tents and continued a march from Tel Aviv to Jerusalem, where they plan to camp outside parliament ahead of the vote.

The judicial overhaul plan was announced shortly after Netanyahu took office as prime minister following November's parliamentary elections.

It was Israel's fifth election in under four years, with all of the votes serving as a referendum on his leadership while facing legal charges.

Critics say removing the reasonability standard would allow the government to appoint unqualified cronies to important positions without oversight.

They also say that it could clear the way for Netanyahu to fire the current attorney general — seen by supporters as a bulwark against the overhaul plan — or appoint legal officials who could ease his way out of the corruption charges he is facing in an ongoing trial.

Netanyahu now heads the country's most ultranationalist and religiously conservative government in Israel's 75-year history.