Israel’s plan to build hundreds of new homes in Jewish settlements in the West Bank and East Jerusalem has drawn a sharp rebuke from Washington.

In a press briefing Tuesday, State Department spokesman John Kirby said the plans “would be the latest step in what seems to be a systematic process of land seizures, settlement expansions, and legalizations of outposts that is fundamentally undermining the prospects for a two-state solution.”

He added: “We oppose steps like these, which we believe are counterproductive to the cause of peace.”

The remarks come after U.N. Secretary-General Ban Ki-moon denounced the intended settlements as “illegal under international law.” In a statement, Ban urged the Israeli government “to halt and reverse such decisions in the interest of peace.” He also said that “legitimate questions” could be raised about “Israel’s long-term intentions, which are compounded by continuing statements of some Israeli ministers calling for the annexation of the West Bank.”

According to the Associated Press, the Israeli plans involve the building of 560 new homes in Ma’ale Adumim, just outside Jerusalem, as well as construction in the Jerusalem neighborhoods of Ramot, Gilo and Har Homa. Some 600 new homes will also be built in an Arab neighborhood of East Jerusalem.

Israeli officials say the construction is necessary as a response to a series of deadly Palestinian attacks against Jewish settlers. In the latest attack, a 13-year-old girl, who was also a U.S. citizen, was stabbed to death in her bedroom in the West Bank community of Kiryat Arba by a 19-year-old Palestinian. The assailant was subsequently killed.

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