ERBIL, Iraq, Sept. 18 (UPI) -- The U.S. ambassador to Iraq and the president of Iraqi Kurdistan addressed tensions between the Kurds and Baghdad as well as constitutional and security issues.

Ryan Crocker met with Kurdish President Massoud Barzani to discuss pushing provincial elections forward in Iraq and the long-term security arrangement set to replace the expiring U.N. mandate for Iraq.

Crocker noted that negotiations between Washington and Baghdad were still under way on the deal, but significant steps had been made.

"We have made very good progress; there are still some issues outstanding," he said.

Regarding the implementation of Article 140 of the Iraqi Constitution, which seeks to settle whether the oil-rich city of Kirkuk is included in Kurdistan or greater Iraq, the U.S. envoy said the matter deserved the utmost diplomatic attention of Iraqi lawmakers.

"We think this needs to be done as a political process in a way that takes into account the concerns and the rights of all the people involved. This has to be an Iraqi process," Crocker said.

Barzani, for his part, addressed cooperation with Baghdad, noting that resolving outstanding issues in the constitution would bring great progress toward the goal of national reconciliation.

"It is natural to have political differences. But we are committed to the constitution, and we will always resort to the constitution when we face problems," he said.