Under the peace blueprint that US President Donald Trump announced in January, Israel has said it intends to extend its sovereignty to Jewish settlements and the Jordan Valley in the West Bank, in up to 30% of the territory.
Palestinians, who have rejected the Trump proposal, seek to establish a state in the West Bank and Gaza Strip, with East Jerusalem as its capital. Israel captured those areas in a 1967 war and withdrew soldiers and settlers from Gaza in 2005.
Palestinian leaders, the United Nations, European powers and Arab countries have all denounced annexation and consider settlements that Israel has built on occupied land as illegal.
Israel disputes this, citing biblical, historical and political roots in the West Bank.
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".