The Washington Times points to some of the evidence.

The attempted Christmas Day underwear bombing of Northwest Flight 253 may have Iranian fingerprints, but those are dots the Obama administration doesn’t want to connect.

Iran and al Qaeda have made mutual war on America in Yemen before. In November 2008, Western security officials intercepted a letter signed by bin Laden deputy Ayman al-Zawahiri thanking Iran for its “vision” in helping al Qaeda establish a foothold in Yemen after being routed from Iraq and Saudi Arabia. The terror leader praised Tehran for its “monetary and infrastructure assistance” related to a September 2008 attack on the U.S. Embassy in Yemen’s capital Sana’a. Sixteen people were killed in the attack, which featured machine gun and rocket fire supporting a double suicide car bombing. …

Some intelligence analysts downplay the idea of cooperation between al Qaeda and Iran because the two are ideological foes. But both detest the United States and have mutual interest in collaborative efforts that hurt U.S. interests. Iran has provided a safe haven – Tehran calls it “house arrest” – to scores of al Qaeda operatives since the terrorist attacks of Sept. 11, 2001. One of Osama bin Laden’s wives, six children and 11 grandchildren are reportedly living in Iran. Former Guantanamo detainee No. 372, Said Ali al-Shiri, who like al Awfi joined al Qaeda in Yemen after Saudi deprogramming, had been in Iran shortly before being picked up by Coalition forces in 2001. Al Shiri was reportedly killed in an air strike in Yemen in December 2009 and may have been one of the planners of the attempted Flight 253 underwear bombing.

Iran has durable ties to the Shi’ite Houthi rebels operating in North Yemen, who are linked to al Qaeda according to Ali Mohamed al-Ansi, director of the Yemeni National Security Bureau. Yemen has seized vessels with Iranian crews smuggling arms to the country, and Yemeni officers involved in weapons trafficking have confessed to Iran’s involvement. In November, Houthi rebel leaders met in Yemen with an official from the Iranian Revolutionary Guard Corps and leaders of Tehran-backed Hezbollah, which reportedly is active in Yemen.

On Dec. 23, Yemeni House Speaker Shaykh Yahya Ali al-Rai said in an interview with the Saudi press that Iranian support for insurgents in Yemen was “beyond any doubt” and that “Iranian interference aims primarily at transforming Yemen into an arena for settling political scores.” Tehran most likely seeks to make Yemen an arena for the kind of proxy wars already being waged in Lebanon, Gaza, Iraq and Afghanistan.