British Prime Minister Boris Johnson is seen on Downing Street, in London, Oct. 29, 2019. Photo: Reuters / Yara Nardi.

British Prime Minister Boris Johnson cautioned Israel on Wednesday against annexing parts of the West Bank, saying it would violate international law and harm its drive to improve relations with the Arab world.

Israeli leaders decided in May that a cabinet debate on annexation could begin from July 1, raising speculation the government would convene on that date.

But with no agreement yet with Israel‘s main ally Washington on the scope and timing of the move, and talks ongoing, no cabinet session was scheduled for Wednesday.

“Annexation would represent a violation of international law,” Johnson said in an opinion piece for Yediot Ahronot, Israel’s top-selling daily, echoing remarks he made in parliament last month.

“Annexation would put in jeopardy the progress that Israel has made in improving relationships with the Arab and Muslim world,” Johnson wrote, calling for a solution that allows justice and security for both Israelis and Palestinians.

Johnson, whose maternal great-grandfather was a Moscow-born Jew, said he had once worked in an Israeli kibbutz during his youth.

In the opinion piece, he said he has been “a passionate defender of Israel.”