U.S. Vice President Joe Biden held talks on Sunday with Iraqi leaders on how to overcome obstacles hampering the formation of a new government after four months of the country's March 7 parliamentary elections.

During separate meetings with Prime Minister Nuri al-Maliki and his rival ex-premier Ayad Allawi, visiting Biden stressed his country's support for democracy in Iraq, an Iraqi official said on condition of anonymity.

Allawi's Iraqia List said in a statement obtained by Xinhua that Allawi and Biden discussed Iraq's political process.

"Allawi reviewed with Biden the talks that carried out by the Iraqia bloc with the other political blocs, stressing the right of the list as the vote-winner to form the next government according to the constitution," the statement said.

Earlier Sunday, at one of former Iraqi leader Saddam Hussein's palaces, Biden and his wife Jill Biden, officiated an Independence Day naturalization ceremony in honor of 156 service members who earned their U.S. citizenship through service.

"This nation, once embroiled in sectarian strife and violence, is moving toward a lasting security and prosperity with a government that represents the interest of every member of the community in Iraq," Biden told a crowd of U.S. service members, according to a press release from the U.S. military obtained by Xinhua.

"When the new government is formed, it will mark something absolutely extraordinary: a peaceful transition of power encompassing all the people of Iraq," he added.

On Saturday, Biden arrived in Baghdad on an unannounced visit for two missions: to celebrate the July 4 weekend with U.S. troops and put pressure towards the formation of an Iraqi government.

Biden's visit came amid ongoing political deadlock over the formation of the next government nearly four months after the country's parliamentary polls.

Late Friday, Iraqi President Jalal Talabani met with a visiting U.S. congressional delegation, which comprised John McCain, Joseph Lieberman, Lindsey Graham and Mark Udall. The meeting focused on Iraq's current political, security and economic situation, according to a press release by the Iraqi presidency.

Nearly four months after the war-torn country held its landmark parliamentary elections, Iraqi political leaders are still wrangling over who will head the next government, leaving the formation of the new government in a deadlock.

The U.S. forces last year have pulled out of Iraqi cities and are working to formally end combat operations by Sept. 1.