The United States and Iran held "frank and serious" expert-level talks on security issues in Iraq on Monday, more than two weeks after a rare meeting between the ambassadors of the two countries who wield the greatest influence over the wartorn country. Washington has accused Teheran of fueling the violence by arming and training Shi'ite extremists, but it agreed during the July 24 ambassadorial talks to set up a security subcommittee to carry forward talks on restoring stability in Iraq. The detention of four Iranian-Americans in Iran has deepened tensions between Washington and Teheran, whose relations were already strained over Iran's nuclear program and its support for terror groups like Lebanon's Hizbullah and the Hamas and by US military maneuvers in the Persian Gulf. Washington has called for their release and says the charges are false. A US Embassy spokesman, Lou Fintor, said Monday's discussions were "frank and serious" and focused on the violence plaguing Iraq. He said the American delegation was led by the US Embassy's counselor for political and military affairs Marcie B. Ries. "We agreed to continue our discussions at a date to be established through diplomatic channels," Fintor said. "We appreciate the role played by the government of Iraq in chairing the meeting." An Iranian Foreign Ministry official, Hossein Amir Abdollahian, headed the Iranian delegation, the official Islamic Republic News Agency reported. Iraqi president Jalal Talabani hosted the sides, who sat at three separate conference tables in an Iraqi government office. "His Excellency expressed hope that the long-awaited Iranian-Iraqi-American meeting will succeed in achieving security and stability in Iraq," Talabani's office said in a statement. "The president hopes that Iran will play a positive role in finding a way to achieve the ambitions of the Iraqi people." Iran holds considerable sway in Iraq, where the majority of the population is also Shi'ite Muslim and where Shi'ite political parties have close ties to Teheran. Iraqi Prime Minister Nouri al-Maliki was slated to visit the Islamic republic on Wednesday, a day after a trip to Turkey. His government has said it wants good relations with Iran while insisting there should be no interference in its internal affairs. The US ambassador to Iraq, Ryan Crocker, and his Iranian counterpart Hassan Kazemi Qomi agreed to establish the security committee during a second in a series of rare meetings July 24. The first round of Iran-US talks, on May 28 in Baghdad, broke a 27-year diplomatic freeze following the 1979 Islamic Revolution and US Embassy takeover in Teheran. Former US Ambassador Zalmay Khalilzad saw Iranians on the sidelines of a Middle East meeting earlier this year and both he and Crocker met privately with Iranians over Afghanistan after the Sept. 11, 2001, attacks when the US was headed into Afghanistan to depose the Taliban.