Jordan Valley, a strategic plain with key resources
Israel considers control of the plain, which sits between two desert mountain ranges, essential for its security.
If Israel presses ahead with annexation, the valley will mark the country's western border with Jordan.
The kingdom is just one of two Arab nations, along with Egypt, to have a peace deal with Israel.
But the Israeli military sees the sparsely populated valley as a potential buffer zone in case of ground attacks.
Prime Minister Benjamin Netanyahu in January described it as "vital" to Israel, vowing his government would "apply sovereignty" to the area.
For the Palestinians, such a step would destroy "all chances of peace".
Netanyahu has said annexation would exclude Palestinian population hubs such as the city of Jericho, which risks becoming an enclave surrounded by Israeli territory under the plan.
- Controlled by Israel -
Around 10,000 Israeli settlers live in the Jordan Valley, out of more than 450,000 in the entire West Bank, according to figures from NGOs and the Israeli government.
The valley is home to some 65,000 Palestinians, including around 20,000 Jericho residents, according to Israeli anti-occupation organisation B'Tselem.
Israeli settlements are viewed as illegal under international law, but Washington broke with this consensus in November and said it should be up to Israeli courts to decide on their legality.
Area C covers around 60 percent of the West Bank, while Area B, which accounts for roughly 22 percent, is under Palestinian civil rule but Israeli security control.
The remaining Area A, which covers the eight major towns and cities including Jericho, is under full Palestinian control.
Lying south of Lake Tiberias and to the north of the Dead Sea, the Jordan Valley is also strategic for its agricultural land and water resources in the arid region.
But 85 percent of the valley is inaccessible to Palestinians, according to B'Tselem, while 56 percent is designated for military use.
Israel frequently demolishes Palestinian property built in Area C without Israeli permits, which are extremely hard to obtain.
The Jordan Valley accounts for the highest number of such demolitions in the West Bank, with some 2,400 structures levelled since 2009, according to European Union figures.