A newly named spokesman for two Iraqi insurgent groups yesterday asked the US Congress to make an "official" offer for negotiations with Washington, according to an interview broadcast on Al-Jazeera television. "We will accept nothing but an official initiative from the US Congress with a precise timetable and a binding decision. Let this be clear," Ibrahim Youssef al-Shammari said, speaking on behalf of the Islamic Army in Iraq and the Army of the Mujahedeen.An unverified statement posted on the Internet in the name of the two insurgent groups announced the appointment of Shammari as joint spokesman following Washington's admission it had held talks with rebel representatives. Asked if secret negotiations had begun between rebels and US authorities in Iraq in an attempt to negotiate an end to the insurgency, Shammari denied any dialogue with US forces but was less clear as to whether unofficial contacts had been made. "I deny the existence of a dialogue... All initiatives on these negotiations will be done according to our political program... and no contact of this kind has taken place directly or indirectly with the Americans," he said to the Qatar-based channel.