Iran's supreme leader on Tuesday urged Arab and Muslim nations to be vigilant and stay united to stave off what he described as the "treacherous plots" of the United States and Israel.
"Today, what is considered a success for the American administration and the Israeli regime is a loss to all Islamic nations," Ayatollah Ali Khamenei told worshippers in a televised speech marking the start of the Muslim Eid ul-Fitr holiday.
Iran accuses the United States of destabilising Iraq and condemns Washington for supporting Israel in its occupation of Palestinian territories and the war in Lebanon.
The Islamic Republic has not recognised Israel's right to exist since the 1979 revolution that toppled the monarchy.
Washington broke ties with Iran shortly after the revolution.
"All the nations should be vigilant. Our nation, the Lebanese, Palestinian and Iraqi nations, the nations in the region, and other Muslim nations should be vigilant," Khamenei said, adding that they should all "retain their national unity".
"They should be cautious not to make a move which is in line with the fulfilment of the new hostile treacherous plots of the Americans and the Zionism," he said
The United States accuses Iran of backing insurgents in Iraq and of sponsoring terrorism, including the Palestinian group Hamas and Lebanon's Shi'ite Muslim Hezbollah group, both of which the Washington brands terrorist.
Israel also accuses Iran of backing terrorism and of threatening the Jewish state with its nuclear programme, which the West says is aimed at building atomic bombs despite Iranian denials.