A US military spokesman said Wednesday that Shi'ite-dominated Iran is providing support to some Sunni insurgents fighting American forces in Iraq. Maj.-Gen. William Caldwell said the military had credible intelligence to support the allegation but did not elaborate. He said the support to Sunni insurgents was limited to select groups, which he did not name. "It's not all Sunni insurgents, but rather we do know that there is a direct awareness by Iranian intelligence officials that they are providing support to some select Sunni insurgent elements," Caldwell told reporters in Baghdad. On Sunday, a US general also said powerful armor-penetrating roadside bombs believed to be of Iranian origin were turning up in the hands of Sunni insurgents south of Baghdad.