Speaking to an audience of Iranian officials and ambassadors of Muslim countries to Iran, Khamenei stressed that "Zionists" would be unable to achieve their goals, and that Palestine would be finally liberated.
US President Donald Trump is expected to announce on Wednesday that the United States recognises Jerusalem as the capital of Israel and will move its embassy there, breaking with longtime US policy and potentially stirring unrest.
Jerusalem remains at the core of the Israel-Palestine conflict, with Palestinians hoping that East Jerusalem - now occupied by Israel - might eventually serve as the capital of a future Palestinian state. Iran has long supported a number of Palestinian militant groups in their fight against Israel.
Iranian President Hassan Rouhani denounced as "provocative and dangerous" the USA decision to recognize Al-Quds (Jerusalem) as the Israeli regime's capital, calling for concerted action by Muslim and peace-loving nations to defy such an illegal measure.
The US provocative decision to recognize the city of Quds as the integrated capital of the Zionist regime will not bring peace and stability to the region, and on the contrary, it will reveal US government's intentions and discredit this country's claims in the eyes of parties who still believe in the US impartiality in the peace negotiations.
During a phone conversation with his Turkish counterpart Recep Tayyip Erdogan, Rouhani called on Islamic states to join hands in opposing the "dangerous" move by the Trump administration.
"Iran strongly condemns this move and urges the global community, influential countries and especially Islamic countries to prevent the implementation of this USA action, which is only of benefit to the Zionist regime, to preserve the stability of the region".
The Iranian president went on to say: "We have to be aware and ready in the face of the USA, the Zionist entity and their tails".