CAIRO (AFP) - Al-Qaeda chief Ayman al-Zawahiri has accused the United States of "plotting" with the Egyptian military, secularists and Christians to overthrow Egypt's Islamist president Mohamed Mursi, in an audio recording posted on militant Islamist forums.

Speaking of the July 3 military coup, Zawahiri, himself an Egyptian, said: "Crusaders and secularists and the Americanised army have converged ... with Gulf money and American plotting to topple Mohamed Mursi's government."

He accused Egypt's Coptic Christian minority of supporting the Islamist president's ouster to attain "a Coptic state stripped from Egypt's south."

The recording contained the militant leader's first public comments on Mr Mursi's ouster.