Using his official Twitter account, the Iranian Supreme Leader tweeted on Tuesday, "Trump's 'Deal of the Century' will die earlier than Trump himself."
Trump recently unveiled his plan promising to keep Jerusalem as Israel's undivided capital, and proposes an independent Palestinian state and the recognition of Israeli sovereignty over West Bank settlements.
"The Americans and the Israelis have made a deal over something that does not belong to them," Khamenei said, adding that "Palestine belongs to the Palestinians, and they should decide on it."
"We believe that the armed Palestinian groups will continue their resistance, and this is the duty of the Islamic republic to support the Palestinian groups," he added.
The only way for peace and to settle the issue of Palestine is to refer to the "free vote" of Palestinians regardless of their religion, he stressed.
Trump's so-called "deal of the century" has been rejected by the Arab League and several other nations around the world; however, the U.S. President has refused to abandon this initiative.
The Palestinian leadership has rejected the peace plan and threatened to cutoff all ties with the United States if they do not withdraw the proposal.
Trump's peace plan calls for Israel's annexation of the Jordan Valley, along with recognizing Israel's illegal settlements in the occupied West Bank. In turn, Trump has offered the Palestinians statehood, with a shared capital in Jerusalem.