Iraqi Prime Minister Nouri al-Maliki appealed to Iran on Wednesday for greater cooperation in easing his country's violence, even as the United States has stepped up accusations that Tehran is arming Iraqi Shiite militants. Al-Maliki's Shi'ite-led government is closely tied to predominantly Shi'ite Iran and has been reluctant to openly embrace the US claims against Teheran. Instead, Baghdad has been struggling to strike a balance between the bitter rivals, the two countries with the largest sway over Iraq. The Iraqi prime minister's visit to Tehran came two days after US and Iranian experts held talks in Baghdad on improving Iraq's security. Iraqi officials would not say if al-Maliki, on his second trip to Tehran in the past year, would directly press Iran on the U.S. accusations during his talks with Iranian leaders. Iraqi government spokesman Ali al-Dabbagh said the visit aimed to boost agreements making Iran "a positive base" in support of Iraq. Al-Maliki and Iraqi officials gave few details on what sort of security cooperation they were seeking from Iran during his visit, expected to last three days. The trip also aimed to tighten already growing economic ties between the two countries. "We want to promote economic ties and other ties that contribute to combating terrorism and its challenges," al-Maliki told The Associated Press on the plane to Iran. Al-Maliki later met with President Mahmoud Ahmadinejad. The two leaders walked into an ornate meeting room holding hands, then shook for the cameras before beginning their talks. Several other Iraqi and Iranian officials also attended the closed meeting. Al-Maliki also was to meet later in his trip with Iranian supreme leader Ayatollah Ali Khamenei. The visit comes at a time when the US military is increasing its accusations that Iran is fueling Iraq's violence. Lt. Gen. Raymond Odierno, the US second-in-command, said Sunday that Iranian-armed Shiite militiamen were behind 73 percent of the attacks that killed and wounded US troops in Baghdad in July, nearly double the figure six months earlier. Iran has denied arming or financing Shiite militias. Al-Maliki's government has said only that it does not "rule out" Iranian involvement. During his visit, al-Maliki met with Iranian Vice President Parviz Davoodi and "asked Iran for real security cooperation," an al-Maliki aide said, speaking on condition of anonymity because he wasn't authorized to speak to the media. Davoodi told al-Maliki that "Iran has been always paying attention to providing and improving security in Iraq," according to the Iranian state news agency IRNA. Davoodi also promised Tehran's "support for a strong and cohesive coalition" government in Iraq, as well as backing for al-Maliki personally, the al-Maliki aide said. But such Iranian backing would likely only further alienate Iraq's Sunni Arab politicians. Sunni Arab parties have fled al-Maliki's coalition in recent days - either dropping out of the government or boycotting his Cabinet - in a blow to US efforts to get them to work together on political reform. Iraq's Sunni Arab minority are also deeply suspicious of the Shiite and Kurdish leadership's close ties with Iran - as are mainly Sunni Arab governments in the region. In Syria, meanwhile, officials from Iraq and its neighbors, including Iran, held a conference Wednesday on improving Iraq's security. Iraq's Deputy Foreign Minister Labib Abbawi pressed countries to do more to stop the infiltration of fighters and weapons over their borders into Iraq. Syria has been the target of frequent complaints from the U.S. and Iraq that it is not doing enough to stop fighters and weapons from reaching Iraq. The al-Maliki aide said the Iraqi prime minister was hoping to visit Syria in the coming days for security talks.