Al-Qaeda chief Ayman al-Zawahiri has ruled that the Islamic State of Iraq and Al-Nusra Front in Syria should operate as separate entities, according to a letter posted on Al-Jazeera television\'s website. ISI leader Sheikh Abu Bakr al-Baghdadi had \"made a mistake\" by announcing a merger between the two radical Islamist groups in the neighbouring Arab states\"without consulting us,\" he said. The merger plan has been \"damaging to all jihadists\", Zahawari said, adding that \"Al-Nusra Front is an independent branch of Al-Qaeda\". Zawahiri ordered ISI and Al-Nusra to \"cease all hostilities towards each other\" and to help each other \"in terms of men, money and weapons\". He also appointed cleric Abu Khalid al-Suri as his representative in Syria to arbitrate on any issues resulting from the cancellation of the merger of the two wings. The authenticity of the letter which Al-Jazeera said it obtained from \"reliable sources in Syria\" could not be independently verified. In early April, Baghdadi said that Al-Nusra Front was ISI\'s branch in Syria and the ISI would be renamed the Islamic State in Iraq and the Levant. Al-Nusra leader Abu Muhammad al-Julani acknowledged the relationship but rejected the merger and criticised Baghdadi for his announcement. The declaration caused a stir among jihadists fighting the regime of Syrian President Bashar al-Assad, leading Julani to publicly pledge his allegiance to Zawahiri. In a reaction on Twitter to mediation by Zawahiri, Julani expressed his \"respect\" for Baghdadi and readiness to cooperate in \"confronting the enemies of God\". Al-Nusra Front, created in January 2012, joined Al-Qaeda last December on a US list of foreign terrorist organisations. It has carried out some of the deadliest attacks in the uprising against the Syrian regime, claiming responsibility for several suicide bombings.