TEHRAN, Iran — Iran’s supreme leader called on all Muslims to support the Palestinian people in their opposition to the Trump administration’s “deal of the century” Middle East peace plan.

Ayatollah Ali Khamenei, in a letter a week ago today marking the Islamic hajj pilgrimage, said the still-unreleased U.S. plan was a “ruse” that’s “doomed to failure.”

He also called for “active participation” in efforts to block the U.S. plan, which faces deep skepticism from the Palestinians because of policies they see as biased toward Israel.

The Trump administration plan centers on a $50 billion Palestinian investment and infrastructure proposal, but avoids core political issues that are key to resolving the dispute.

This year’s hajj pilgrimage in Saudi Arabia comes amid heightened tensions in the nearby Persian Gulf between the U.S. and Iran.