BETHLEHEM (Ma'an) -- Israel on Wednesday threatened "difficult and far-reaching consequences" of plans to upgrade Palestine's status in the United Nations next month.

Israeli Foreign Minister Avigdor Lieberman relayed the warning during talks with visiting EU foreign policy chief Catherine Ashton in Jerusalem, a statement from his office said.

If President Mahmoud Abbas "continues unilateral measures against Israel in the UN General Assembly, there will be difficult and far-reaching consequences," Lieberman told Ashton.

Lieberman has repeatedly criticized Abbas' refusal to negotiate with Israel until Prime Minister Benjamin Netanyahu agrees to freeze settlements. Lieberman is a settler.

In Ramallah on Wednesday, Abbas said he would be ready for negotiations with Israel "straightaway" if the UN recognized Palestine as a non-member state.

"We have resolved to go to the UN to save the two-state solution and to achieve the rights of our people as an observer state," Abbas told reporters during a visit by the Bulgarian president.

"We're ready to go back to negotiations straightaway. Going to the UN is not a substitute for negotiations. We are in need of negotiations to solve the final status of issues that face us both."

If the UN bid succeeds, Palestine's "observer entity" status would change to "observer state", granting access to bodies such as the International Criminal Court.

The Palestinians need a simple majority for the upgrade, but predict that between 150 and 170 nations will vote in favor.