US and Iranian envoys exchanged direct talks Saturday at a conference on Iraq stability efforts to open possibly groundbreaking steps that could ease their nearly 28-year diplomatic freeze. The US ambassador to Iraq, Zalmy Khalilzad, said he exchanged views with Iranian delegation "directly and in the presence of others" at the one-day meeting of Iraq's neighbors and others including the five permanent members of the UN Security Council. He declined to give details of the contacts - calling them only "constructive and business-like and problem-solving" - but noted that he raised Washington's assertions that Shi'ite militias receive weapons and assistance across the border from Iran. Khalilzad called it a "first step." "The discussions were limited and focused on Iraq, and I don't want to speculate after that," he said. For Iran, opening more direct contacts with Washington could help promote their shared interests in Iraq, including trying to stamp out Sunni-led insurgents. US officials, meanwhile, need the support of Iranian-allied political groups in Iraq to keep a lid on Shi'ite insurgents. Washington broke off ties with Iran after militants occupied the US Embassy in Teheran in the wake of the 1979 Islamic Revolution. Iraq's foreign minister, Hoshyar Zebari, told reporters there were "direct exchanges and meetings and discussions" between the US and Iranian delegation. He also said the participants at the meeting agreed to take part in future groups to study ways to bolster Iraq's security, assist displaced people and improve fuel distribution and sales in one of OPEC's former heavyweights. Zebari did not say whether Iran and the United States could join in these smaller "tactical committees." Iraq's prime minister, Nouri al-Maliki, opened the meeting with an appeal for international help to sever networks aiding extremists and warned that Iraq's growing sectarian bloodshed could spill across the Middle East. Khalilzad also urged nations bordering Iraq - which include Syria and Iran - to expand assistance to al-Maliki's government, saying "the future of Iraq and the Middle East is the defining issue of our time." "[Iraq] needs support in this battle that not only threatens Iraq but will spill over to all countries in the region," al-Maliki said - shortly before mortar shells landed near the conference site and a car bomb exploded in a Shiite stronghold across the city. Al-Maliki urged for help in stopping financial support, weapon pipelines and "religious cover" for the relentless attacks of car bombings, killings and other attacks that have pit Iraq's Sunnis against majority Shi'ites. The delegates proposed an "expanded" follow-up meeting, which could include the G-8 nations and others, in Istanbul, Turkey, next month. Iraqi officials, however, say they will urged that the next meeting take place again in Baghdad. The meeting also gives a forum to air a wide range of views and concerns including US accusations of weapons smuggling from Iran and Syria, and Arab demands for greater political power for Iraq's Sunnis. Security was extremely tight as envoys gathered in Iraq's Foreign Ministry, which is outside the heavily protected Green Zone. Shortly after the meeting began, at least two mortar shells hit near the Foreign Ministry. There were no casualties. Al-Maliki said "the terrorism that kills innocents" in Iraq comes from the same root as terrorists attacks around the world since September 11, 2001, in a reference to groups inspired by al-Qaida. He also delivered an apparent warning to Syria and Iran to stay away from using Iraq as a proxy battleground for fights against the United States. "Iraq does not accept that its territories and cities become a field where regional and international disputes are settled," he said. Khalilzad did not specifically mention Iran in statements to delegates, but he offered indirect messages that Washington acknowledges Teheran's growing influence in the region. "The US seeks an Iraq that is at peace with its neighbors; and neighbors that are at peace with Iraq," he said, according to a text distributed by the US Embassy. But he also reasserted US claims that Syria allows foreign jihadists and Sunni insurgents to cross its border into Iraq, and that weapon shipments from Iran reach Shi'ite insurgent groups. Both nations deny the allegations. "I urge all neighbors to categorically reject the principle that selective violence against certain categories of Iraqis or against coalition and Iraqi security forces is acceptable," he said. Iran has strongly denounced the US military presence even though it toppled their old foe Saddam Hussein. The complaints grew more pointed in December after American forces detained two Iranian security agents at the compound of a major Shi'ite political bloc in Baghdad. Six other Iranians were arrested January 11 at an Iranian liaison office in northern Iraq. The US military said they were members of Iran's elite Revolutionary Guard - a charge Teheran rejects. Khalilzade appeared to address Iran's complaints by saying US-led troops do not "have anyone in detention who is a diplomat." The showdown over Iran's nuclear program also lurks behind any attempt to ease the nearly 28-year diplomatic freeze with Washington. There have been other chances in the past for one-on-one dialogue between the United States and Iran, but rarely with such promise. In September, the United States joined Iran and Syria in talks on Iraq - although Washington ruled out direct talks with Iran in advance. Other tensions issues were part of the meeting. The Arab League said this week that it would urge changes in Iraq's constitution to give more political power to Sunnis, who are outnumbered nearly 3-to-1 by Shi'ites. Many Shi'ites in Iraq saw the statement as a challenge to the legitimacy of al-Maliki's government. Other potential friction at the meeting could come from Turkey, which opposes plans to hold a referendum sometime this year on whether the northern oil hub of Kirkuk will remain in Arab-dominated territory or shift to the semiautonomous Kurdish zone. Turkish officials fear that oil riches for the Kurds could stir separatist sentiments and spill over into Kurdish areas in Turkey. "All the delegates are united by one thing: the fear of a prolonged civil war in Iraq. It would hurt them each in different ways," said Abdel-Moneim Said, director of Al-Ahram Center for Political and Strategic Studies in Cairo. "Fear is the one thing bringing them all together."