Iraq welcomes Vice President Biden's encouraging words about America's commitment to Iraq, but government spokesman Ali al-Dabbagh said Saturday that political reconciliation is an internal matter best handled by Iraqis.

Biden arrived in Iraq on Thursday to visit troops for the July 4 holiday and to also urge Iraq's political, ethnic and sectarian factions to make more progress on divisive issues. The Obama administration recently announced that Biden would overseeing Iraq policy for the U.S. government, part of which included encouraging more political progress from Iraq's leaders.

"Any party that is not Iraqi will not add to the success of this issue," Mr. Dabbagh said of political progress.

Biden began Independence Day by greeting more than 200 U.S. soldiers from 59 countries who were becoming American citizens at a naturalization ceremony in a marble domed hall at one of Saddam Hussein's palaces at Camp Victory, the U.S. military headquarters on the outskirts of Baghdad.

He then had lunch with the 261st Theater Tactical Signal Brigade from Delaware, to which his son, Beau, belongs. Beau Biden stood in the back as his father greeted the troops. In telling the brigade about the naturalization ceremony, the vice president used some of his characteristic colorful language.

"We did it in Saddam's palace,'' he said. "[He] is rolling over in his grave right now.''

Biden met with Iraqi Prime Minister Nouri al-Maliki and other leaders on Friday and planned to see top officials in the Kurdish north on Saturday, but that trip was canceled because of heavy sandstorms.

There are ongoing tensions between the central and Kurdish governments because of claims over disputed territories. Those clashing views intensified last month when the Kurdish parliament approved a new constitution for the Kurdish region that will be voted on by residents at the end of July, when a new Kurdish parliament will also be elected

The proposed new constitution says the oil-rich area of Kirkuk belongs to Kurdistan. Kirkuk is claimed by Arabs, Kurds and Turkomen and has been the scene of large-scale attacks in recent weeks. The document said also parts of Ninewa and Diyala provinces, which are part of the disputed territories also belongs to parliament.

Dabbagh said any legal document that contradicted the Iraqi constitution was cause for concern because the nation's constitution is the highest legal authority.

The issue of disputed territories is being mediated by the United Nations. Biden told Iraqi leaders that if the war-torn country reverted back to sectarian or ethnic military clashes like those seen in 2006 and 2007, it would be difficult to maintain America's current level of engagement, partly because the American public would not have an appetite for it.

On another important issue for Iraq, Dabbagh said the Iraqi government was studying last week's historic oil bid round to ensure that the second one would be more successful. Only one field out of six oil fields and two gas fields were awarded, disappointing oil firms and industry observers in what was billed as Iraq's first opening to Western oil firms in more than 30 years.

Dabbagh said given that the first bid round was a uniquely transparent process for both Iraq and the oil industry, it was beneficial that Iraq managed to get a BP-led consortium to cut its payout in half to $2 a barrel. BP and its minority partner, China National Petroleum Co., won the biggest prize of the auction, the Rumaila field in southern Iraq. Dabbagh also noted strong participation in the oil bids by Chinese energy firms.

Still, Dabbagh said he was aware that because only one oil field was awarded, largely because of the Oil Ministry's aggressively low price demands, the auction was viewed by some as not being as successful as it could have been. The Iraqi government plans to hold the second bid round, originally scheduled for the end of this year, earlier than expected, partly to move quicker on developing Iraq's oil sector.

Eleven undeveloped or partially developed gas and oil fields are part of the second bid round, which could also include five oil fields that weren't awarded in the first auction. In addition to the 35 companies that qualified for the first bid round, nine additional firms are also allowed to participate in the second auction.

"The Ministry of Oil is trying to benefit from the first conference so that the next one is more effective," Dabbagh said.