Jordan's King Abdullah II warned Israel of "disastrous repercussions" if it crosses a "red line" on Jerusalem, in talks on Friday with Spanish Prime Minister Jose Luis Rodriguez Zapatero.
"Jerusalem is a red line and any manipulation in this city would have disastrous repercussions on the security and stability of the region," he said, quoted in a palace statement.
Abdullah urged the international community, especially the European Union, "to act firmly against any Israeli measures aimed at changing the identity of the Holy City of Jerusalem and threaten the places of worship."
The fate of the Holy City, with sites sacred to Christians, Jews and Muslims, is one of the most sensitive issues in the decades-old Middle East conflict.
Israel captured east Jerusalem in 1967 and annexed it in a move not recognized by the international community. It considers the entire city to be its "eternal, indivisible" capital.
The Palestinians want to make eastern Jerusalem the city the capital of their promised state. They are angry over encroachment there by Jewish settlers while accusing the Israeli-run municipality of making it virtually impossible for them to get permits for new homes or extending existing ones.
Zapatero was in Jordan on a regional tour aimed at advancing Middle East peace efforts that has taken him to the Palestinian territories, Israel and Syria. He travelled on to Lebanon.