Saudi Arabia's King Salman arrived in Qatar on Monday as part of a rare regional tour ahead of the annual summit of Arab leaders of the oil-rich Gulf states.The trip comes at the time of a political transition in the United States and as deadly conflicts rage in Syria, Iraq and Yemen.Salman began his tour in the United Arab Emirates, a key pillar of a Saudi-led Arab coalition that has been battling Iran-backed Shia Huthi rebels in Yemen since March 2015.After Qatar, he will travel on to Kuwait and Bahrain, which is to host this year's Gulf Cooperation Council (GCC) summit.His trip excludes Oman, known for its warm ties with the kingdom's regional arch-foe Iran and the only GCC member which is not taking part in the Saudi-led coalition.British Prime Minister Theresa May, visiting the Gulf for the first time since she came to office in July, will attend the two-day GCC summit which begins December 6.