WASHINGTON — A strike by an unmanned drone last week killed a senior commander of Al Qaeda who had played a significant role in planning the killing of Central Intelligence Agency operatives in late December at a base in Afghanistan, according to American officials. The March 8 strike was one of a series aimed at suspected participants in the deadly attack in Khost Province, which took place just before a meeting with a militant who the Americans believed could provide information on Al Qaeda’s operations. Seven Americans and a Jordanian intelligence officer died in that attack. According to a United States counterterrorism official, the Qaeda operative killed last week was Hussein al-Yemeni. The drone missile struck in Miram Shah in North Waziristan, a part of Pakistan where Al Qaeda is considered well dug in.