The White House says it is deeply concerned at what it called the “divisive rhetoric” in the Israeli election, which ended in a surprise win for Benjamin Netanyahu’s Likud party.
During campaigning, Mr Netanyahu said he would not allow the creation of a Palestinian state if re-elected.
The US, UN and EU have all urged him to continue with the two-state solution.
Mr Netanyahu aims to build a new coalition government within two to three weeks, his party says.
White House spokesman Josh Earnest said: “It has been the policy of the United States for more than 20 years that a two-state solution is the goal of resolving the conflict between the Israelis and Palestinians.”
The US would “re-evaluate our approach” in the wake of Mr Netanyahu’s comments ruling out a Palestinian state, he said.
Mr Earnest added that President Barack Obama was yet to congratulate Mr Netanyahu on his win but would do so in the coming days once he had been directed to form a government, as in previous elections.
UN spokeswoman Farhan Haq called on the new Israeli government to negotiate a peace that would create “a viable Palestinian state”.
The EU foreign affairs chief, Federica Mogherini, congratulated Mr Netanyahu on his win and called for the re-launch of the Israel-Palestinian peace process.
Talks have been on hold since the last round collapsed a year ago.
The Palestinian President, Mahmoud Abbas, said he would work with any Israeli government that accepts the two-state solution, without which, he said, peace negotiations stood “no chance”.
Sami Abu Zuhri, a spokesman for Hamas, which controls the Gaza Strip, said it was irrelevant who won the Israeli elections.
“We don’t differentiate between Israeli parties because they are bound to deny our people’s rights and continue the aggression on us,” he said.
With almost all the votes counted, the latest tally gives Mr Netanyahu’s Likud party 30 seats in the 120-seat parliament, the Knesset, with Zionist Union on 24 seats.
Mr Netanyahu has not yet been asked to form a government, but the win makes him most likely to be given the first opportunity by Israeli President Reuven Rivlin.
The win comes as a surprise, as Likud trailed the Zionist Union in the latter stages of the campaign.
Likud said Mr Netanyahu had already spoken to parties he saw as possible coalition partners, including right-wing and ultra-Orthodox parties and the centrist Kulanu, which won 10 seats.
Kulanu’s support is likely to be essential, with its leader Moshe Kahlon offered the post of finance minister by Mr Netanyahu ahead of the vote.