Yemeni tribes are deeply loyal to their people........

Thousands of tribesmen threatened to descend on Yemen s capital to join the battle against forces loyal to President Ali Abdullah Saleh.

 For months, youth-led protesters have tried to drive out Saleh peacefully. But their campaign has been overtaken and transformed into an armed showdown between Yemen s two most powerful families, the president s and the al-Ahmar clan.

The al-Ahmar family heads the country s strongest tribal confederation, which has vowed to topple Saleh after 33 years in power.

 Their nearly two week-old battle in Sanaa raises a dangerous new potential in Yemen: that tribal fighting could metastasize and spread across the impoverished nation. Tribes hold deep loyalty among Yemen s people.