US Defense Secretary Robert Gates urged Middle East nations Saturday to help fight the spread of violent extremism by funding and training Afghan security forces and reaching out more aggressively to the fledgling government in Iraq. Gates also assured a gathering of Persian Gulf leaders here that President-elect Barack Obama will continue the US commitment to the Middle East, including efforts to fight terrorism and develop a two-state solution between Israel and the Palestinians. And as the lone Republican holdover from the Bush Cabinet to the Obama team, Gates issued a public warning that any effort by terrorists to test the new administration would be a mistake because there has been extensive planning to ensure a smooth transition. "Anyone who thought that the upcoming months might present opportunities to 'test' the new administration would be sorely mistaken," Gates said. "President Obama and his national security team, myself included, will be ready to defend the interests of the United States and our friends and allies from the moment he takes office on Jan. 20." Saying that a stable Iraq can play an important role in the region, Gates urged Gulf leaders to set aside old hostilities inflamed in the Saddam era and forge diplomatic ties with Iraq. "All of us have a stake in Iraq's ongoing fight with extremists," Gates said. "Neighbors must lend support and increase their border-control efforts, especially those that have thus far failed to live up to pledges to tighten border crossings." Gates has persistently pressed Middle East nations to provide political, economic and overall support to Iraq, saying that if that country falls back into extremist control it will be a threat to the entire region. On Iran, his speech struck a more reserved tone this year, compared with his sharper criticism in remarks here last year of Teheran as a chaotic and destabilizing threat. He and others have rebuked Iran for helping bolster militants who then cross the border back in to Iraq. Officials have long believed that Iran - at some level - has provided funding and training to insurgents, and supported the delivery of lethal explosives to Iraq. On Saturday, Gates pressed Gulf nations to impose sanctions on Iran but added that they can be even more influential "by welcoming the new Iraq into the Arab fold." Withholding support for the country, he said, increases the risk that Iraq will be overcome by Iranian influence that has already cost many lives. He offered a similar message on Afghanistan, saying that a failed state there will increase the chances that al-Qaida and other extremists will take hold again - a threat that would stretch across the Middle East and beyond. "An enduring requirement is the ability to rapidly train, equip, and advise Afghan security forces," said Gates, asking that Gulf nations fund and send forces - including engineers and agricultural experts. Gates spent much of the day Thursday in Afghanistan meeting with commanders. He has endorsed plans to add at least 20,000 more US troops to the fight there. A senior military official traveling with Gates said Friday that the major combat units that will be sent to Afghanistan have been identified, but Gates has made no final decisions. The official spoke on condition of anonymity because the deployment decisions have not been announced. Gates also held private meetings in Manama on Friday with officials from the Gulf Cooperation Council, which is made up of the six oil-rich nations of Saudi Arabia, Bahrain, Kuwait, Oman, Qatar and the United Arab Emirates.