due to arrive in Sana'a on Thursday to convey a letter from Emir of Qatar Hamad bin Khalifa al-Thani to President Ali Abdullah Saleh.Well-informed sources were quoted by the state-run 26september weekly as saying that the letter would include an invitation to President Saleh to take part in the 21st Arab summit to be held in Qatar on 30 March.The invitation will also include the attendance of the 2nd Arab-Latin America states Summit which is scheduled to be held in Doha on 31 March.Meanwhile, Arab Foreign Ministers have discussed in the Egyptian capital Cairo the 21st Arab summit's agenda which includes a number of issues relating to politic, economic and security fields.