Top US diplomat Richard Holbrooke had a brief but cordial meeting with Iran's deputy foreign minister Tuesday at an international conference on Afghanistan, marking another step in unlocking 30 years of tense relations. The meeting between Holbrooke, US Secretary of State Hillary Rodham Clinton's special envoy to Afghanistan and Pakistan, and Iran's Mehdi Akhundzadeh came on the sidelines of a meeting where Iran pledged to help the reconstruction of its neighbor but criticized US plans to send more troops into Afghanistan. Holbrooke's meeting "did not focus on anything substantive. It was cordial, it was unplanned and they agreed to stay in touch," Clinton told reporters as the day-long conference was winding down. The gathering was being closely watched for signs that the US and Iran can work together on a common problem after years of hostility. The two countries cooperated in 2001 and 2002 after US-led forces ousted Afghanistan's Taliban government. But relations were frozen during the administration of George W. Bush, who referred to Iran as part of the "Axis of Evil," although Bush's former Secretaries of State Condoleezza Rice and Colin Powell had informal contacts with Iranian foreign ministers. Washington broke diplomatic ties with Teheran after the US Embassy was overrun and diplomats taken hostage during the 1979 Islamic Revolution, which brought to power a government of Islamic clerics. Clinton said she also sent Iran a direct letter concerning three US citizens unable to return from Iran: Robert Levinson, Roxana Saberi, Esha Momeni. Their return would be a humanitarian gesture, the letter said. Normally, US-Iran contacts are conducting through Swiss intermediaries. The private meeting between the US and Iranian officials was the first sign of cordiality at the conference. Although they sat at the same horseshoe-shaped table, neither Clinton nor Akhundzadeh made mention of the other in their speeches Tuesday. The US and Iran were among more than 80 countries summoned at the initiative of the United States to focus on Afghanistan. It comes days after Obama unveiled a revamped US policy calling for another 17,000 troops, 4,000 military trainers for Afghan security forces, and hundreds of civilians to assist in Afghanistan's development. "The range of countries and institutions that are represented here shows the universal recognition that what happens in Afghanistan matters to us all," Clinton told the gathering. Iran highlighted its history of helping Afghanistan with cash and infrastructure development and by sheltering 3 million Afghan refugees. The two countries share a 600-mile border. "Iran is fully prepared to participate in the projects aimed at combating drug trafficking and the plans in line with developing and reconstructing Afghanistan," Akhundzadeh said. However, Iran was critical of Obama's plan to send more US troops to Afghanistan, saying those funds instead should be redirected to building Afghanistan's own forces. "The presence of foreign forces has not improved things in the country, and it seems than an increase in the number of foreign forces will prove ineffective, too," Akhundzadeh said. Clinton said one goal of the revised US strategy was to strengthen Afghan security forces. "Security is the essential first step. Without it, all else fails. Afghanistan's army and police will have to take the lead," she said, adding they must be supported by the NATO-led international force. The US contributes about half of the force's 70,000 troops. Afghan President Hamid Karzai and Clinton said Afghanistan would welcome Taliban fighters who embrace peace, reject al-Qaida and pledge to abide by the Afghan constitution. Clinton said most Taliban fighters have allied with anti-government forces "out of desperation" rather than commitment, in a country that has barely made inroads against poverty and lack of development. "They should be offered an honorable form of reconciliation and reintegration into a peaceful society, if they are willing to abandon violence, break with al-Qaida, and support the constitution," Clinton said. The United States is starting cautiously down a path in Afghanistan that proved helpful in Iraq, where former insurgents joined forces with US troops and a US-backed government. Although the conference was devoted to Afghanistan, Clinton said it should also focus attention on the lawless border regions of Pakistan that provide a safe haven for the insurgents. "Our partnership with democratic Pakistan is crucial. Together, we must give Pakistan the tools it needs to fight these extremists," Clinton said. Pakistani Foreign Minister Shah Mahmood Qureshi, however, warned against interfering in his country. A regional approach to Afghanistan must include "respect for sovereignty, territorial integrity and non-interference," he said. Akhundzadeh, too, cautioned against losing sight of the conference's objectives of providing security and reconstruction for Afghanistan, and urged countries to "refrain from any kind of deviation from this motto." In a closing statement, the conference agreed to promote good governance and stronger institutions in Afghanistan while generating economic growth and strengthening security. It pledged to support the Afghan army and police, which it said is "undergoing a comprehensive reform." Karzai said any increase in military action against the insurgents must avoid further civilian casualties. He also pledged a renewed campaign against the endemic corruption that riddles the Afghan bureaucracy, and against the narcotics trade that finances al-Qaida operations. The Obama administration is less enthusiastic about Karzai than the Bush White House, and Clinton on Tuesday skipped what used to be a ritual praising of his courage and leadership. The two were meeting privately later. "Corruption is a cancer, as dangerous to long-term success as the Taliban or al-Qaida," Clinton said in clear reference to charges of rampant graft and cronyism in Karzai's government. "A government that cannot deliver accountable services for its people is a terrorist's best recruiting tool." Karzai also promised a free and fair vote when he stands for re-election later this year. Clinton pledged $40 million and the European Union promised â‚¬60 million ($79 million) to run and monitor the election. Karzai also pointed out some of his government's achievements: more than doubling per capita income, extending health services, having the highest school attendance in history and having women study in universities - a development "which was unthinkable a few years ago."