TEHRAN: Iran and Qatar on Monday pledged to cooperate for greater regional security during a visit to Tehran by the emir of the Gulf state, state media reported. “By consultation and harmony Iran and Qatar can strengthen unity among regional countries and implement security and stability,” Iranian President Mahmoud Ahmadinejad was quoted as saying in a meeting with Sheikh Hamad Bin Khalifa Al-Thani. Ahmadinejad also described ties between Tehran and Doha as “brotherly and excellent,” state television reported. “Cooperation between Iran and Qatar can guarantee security and stability in the region,” the emir was quoted as saying. It was the first visit by an Arab leader to the Islamic republic since US diplomatic memos from Arab countries in the Gulf were released by whistle-blower WikiLeaks late last month, uncovering a fixation on the Iranian nuclear threat. But a leaked memo revealed that Sheikh Hamad had dismissed the threats of proliferation, saying they were made only to scare Iran. Iran insists its nuclear program is entirely peaceful, but world powers suspect Tehran is working toward an atom bomb. Meanwhile, Iranian Supreme Leader Ayatollah Ali Khamenei said on Monday any findings by an international tribunal into the 2005 assassination of former Lebanese Prime Minister Rafiq Hariri would be invalid. “This tribunal is a rubber-stamp one whose verdict is null and void whatever it is,” state television quoted Khamenei as saying during a meeting with the emir of Qatar. Iran is a supporter of Hezbollah, the Lebanese Shi'ite group which says the tribunal is a tool of Israel aimed at discrediting it by blaming its members for Hariri's murder.