Thousands of Palestinians protested Wednesday in Gaza against Israel's West Bank annexation plans, as Prime Minister Benjamin Netanyahu said talks were ongoing on the controversial project facing intensifying international opposition.

Netanyahu's centre-right coalition government had set July 1 as the date from which it could begin implementing US President Donald Trump's Middle East peace proposal.

While no major announcement was expected on Israel's self-imposed kick-off date, Netanyahu's office said talks with US officials "were continuing on the application of sovereignty."

Netanyahu was also discussing annexation with his security chiefs, it added, noting that "further discussions will be held in the coming days."

In Gaza City, several thousand protesters gathered, some brandishing Palestinian flags and placards condemning Trump at a rally.

"The resistance must be revived," Gaza protester Rafeeq Inaiah told AFP. "Israel is afraid of force."

Smaller demonstrations were held in the West Bank cities of Ramallah and Jericho, attended by a handful of left-wing Israeli politicians opposed to annexation. 

"We want to affirm our support for peace," former Labour party official Ophir Pines-Paz told AFP.

The Trump plan, unveiled in January, offered a path for Israel to annex territory and Jewish West Bank settlements, communities considered illegal under international law.

Netanyahu supports the Trump plan -- which has been roundly rejected by the Palestinians -- but the right-wing premier has not laid out his intentions for enacting the US proposals.

Hamas, the Islamist group that controls Gaza, fired some 20 rockets from the coastal Palestinian enclave into the Mediterranean Sea on Wednesday, a move aimed at dissuading Israel from moving forward, Hamas sources told AFP.

Hamas, which has fought three wars with Israel since 2008, says that Israeli annexations in the West Bank, which borders Jordan, would be a "declaration of war".

Growing global opposition

Writing in Israel's Yedioth Ahronoth newspaper on Wednesday, Britain's Prime Minister Boris Johnson said that although he was a "passionate defender of Israel," he viewed annexation as "contrary to Israel's own long-term interests."

"Annexation would represent a violation of international law," he said.

Australia, in a rare criticism of Israel, warned against "unilateral annexation or change in status of territory on the West Bank".

France, Germany, several other European states and the United Nations all oppose annexation, as do Gulf Arab states, with which Israel has increasingly sought warmer ties.

Jordan, one of only two Arab nations that has diplomatic ties with Israel, has warned that annexation could trigger a "massive conflict" and has not ruled out reviewing its 1994 peace treaty with the Jewish state.

Amnesty International's deputy Middle East chief Saleh Higazi said: "International law is crystal clear on this matter – annexation is unlawful," adding that if Israel moves forward it "points to the 'law of the jungle.'" 

Domestic opposition

Israel's defence minister and alternate prime minister Benny Gantz has said annexation must wait until the coronavirus crisis has been contained, amid a sharp spike in new Israeli and Palestinian cases.

Israel annexed east Jerusalem following the 1967 Six Day War and then the Golan Heights on the Syrian border in 1981, in moves never recognised by most of the international community.

While some settlers have urged Netanyahu to take similar action in the West Bank, other settlers oppose the Trump plan, as it envisions the creation of a Palestinian state across roughly 70 percent of the West Bank.

"Trump's plan is to establish a Palestinian state in the land of Israel while leaving the Jews with little crumbs," Daniela Weiss, a settler movement leader, told AFP. 

"This thing will not happen. We will not eat this bait. We will not fall into this trap."

Despite mounting headwinds against implementing the Trump plan, experts have stressed that Netanyahu may still move forward in the coming days, noting that he is keenly watching the US presidential election and may be eager to act if he fears the president will not win a second term.

Presumptive US Democratic Party nominee Joe Biden is opposed to any unilateral annexations by Israel.