Such a move would destroy the possibility of a two-state resolution to the Israeli-Palestinian conflict, Mogherini said, adding that settlement construction was already making the idea of two-states impossible.
“If it is not going to be a two-state solution then it is not going to be a solution,” Mogherini said.
Israel captured the West Bank territory from Jordan in the Six Day War, but never annexed it. Area C of the West Bank, where all the Israeli settlements are located, is under Israeli military and civilian rule. Areas A and B are under the autonomy of the Palestinian Authority.
Mogherini’s words come after Prime Minister Benjamin Netanyahu promised earlier this month that if elected, in his next government he would annex portions of Area C of the West Bank.
“The two-state solution is not only fading away," she said. "It is being dismantled piece by piece."
"Abandoning the two-state solution would bring greater chaos, not only to the Holy Land but also to the entire Middle East,” Mogherini continued. “The next escalation of violence in Israel and Palestine could easily spiral out of control, and it would have tragic consequences in a region as unstable as today’s Middle East.”
She said it is “our first duty” to keep the two-state perspective alive, and to preserve the possibility of negotiations.
“But any such plan must be based on the pre-1967 lines with mutually agreed swaps and the status of Jerusalem as the future capital of the two-states,” she said.
Her pledge of support for a two-state resolution to the conflict comes in advance of the anticipated Trump administration’s publication of its peace deal, which it has warned would deviate from the parameters of past efforts toward a two-state solution based on the pre-1967 lines.
“The EU will recognize changes to the pre-1967 borders only if and when agreed by the parties, including with regard to Jerusalem,” she said. “The EU does not recognize Israeli sovereignty over any of the territories occupied by Israel since June 1967, in line with international law and with UN Security Council resolutions 242 and 497.”
She said this same policy applies to the Golan Heights. Mogherini spoke in the aftermath of US President Donald Trump's decision to recognize Israeli sovereignty in the Golan Heights.
Israel captured the territory from Syria in the defensive Six Day War and annexed it in 1981.
Five of the EU countries that sit on the UN Security Council – UK, France, Germany, Belgium and Poland – have clearly denounced the US move, Mogherini said.
“Our position on the Golan Heights has been so clear, because we believe that international rules, international law and international standards must be upheld," she said.
Mogherini is among those that belief that even though Israel acquired the Golan Heights in a defensive war, it cannot retain it.
“Borders cannot be changed by military force,” she continued. “And this is a principle behind which the EU will continue to firmly stand and in a united manner.”