JERUSALEM — With Western support swelling in favor of a Palestinian bid for enhanced status at the United Nations, Israel engaged in damage control on Wednesday, a day before the vote.

Israeli officials began to play down the significance of a draft resolution that calls for the upgrading of the Palestinian status to nonmember observer state from observer, a change that is also opposed by the United States but that is virtually certain to pass. Additionally, Israel has toned down its threats of countermeasures after the vote, aware that a harsh reaction would only isolate it further.

“The United Nations General Assembly will pass a one-sided anti-Israel resolution that should come as a surprise to nobody, and certainly not to anyone in Israel,” said Mark Regev, a spokesman for the Israeli government. “We always said that the reality was that the Palestinians have an automatic majority in the General Assembly.”

While Mr. Regev acknowledged “a certain amount of disappointment” over the decision of some friendly European countries to support the Palestinians or to abstain from the vote, he said: “Ultimately, what we will see at the United Nations is diplomatic theater. It will in no way affect the realities on the ground.”