* U.N. wants special governorate status for Kirkuk
* Diplomat critical of Kurdistan president
BAGHDAD, July 21 (Reuters) - The United Nations is urging Iraqi Kurds not to push for a referendum on whether the Kirkuk oil area should be part of their northern enclave, saying such a vote would ignite conflict, a Western diplomat said on Tuesday.
Lying 250 km (155 miles) north of Baghdad and with 13 percent of Iraq's oil reserves, the disputed region housing rival ethnic Kurds, Arabs and Turkmen is at the heart of a power struggle pitting the Iraqi government in Baghdad against the largely autonomous Kurdistan region to the north.
Kurds claim Kirkuk as their ancient capital, hoping it and other disputed territories can be annexed by the Kurdistan Regional Government (KRG), an idea rejected by Baghdad as well as the city's Arab and Turkmen residents. Kurds want a referendum in Kirkuk, which they think they would win.
Iraq's constitution lays out a plan to determine who controls the region through a referendum and helping displaced families return home, but political feuding has delayed it.
The United Nations believes that such a referendum would be dangerously provocative, perhaps triggering renewed fighting by rival factions just as Iraq approaches stability.
"The U.N. says it will not support a hostile referendum ... (asking) do you want to join the KRG or not?" the diplomat, who is involved in the negotiation, said on condition of anonymity.
"We (all) believe that would lead to war and the U.N. has ... told the Kurds that," he said.
The simmering row between Kurds and Arabs over land and oil is seen as a major threat to Iraq, as the sectarian violence that nearly tore Iraq apart in 2006 and 2007 recedes.
The United Nations, empowered by the Iraqi government to help broker a solution to the impasse, issued a report in April meant to outline possible solutions to the dispute.
These solutions included a new political agreement that would ease implementation of the constitutional plan for Kirkuk, including a census and referendum; another would make Kirkuk a province of Iraq like any other, favoured by Arabs.
Other solutions would make Kirkuk a governorate with special links to both Baghdad and Kurdistan or would give it some autonomy -- a degree of self-rule -- favoured by Turkmen.
All options could be endorsed in a referendum.
The diplomat said the United Nations favoured Kirkuk becoming a governorate but its choice has won few supporters within Iraq so far.
The diplomat spoke of frustration with Kurdish President Masoud Barzani, who vows that Kurds will not give up Kirkuk.
"Barzani is still making extremely provocative remarks ... None of his staff ever say, 'Look, this is dangerous.'"
He attributed some of the Kurds' position to failures by Arab leaders to acknowledge crimes committed by Saddam Hussein.
Baghdad expelled thousands of Kurds and Turkmen from Kirkuk and towns like Khanaqin from the 1970s, and Saddam used poison gas to slaughter Kurds by the thousands in the 1980s.
Barzani's office was not immediately available for comment.
The census and referendum on the status of disputed territories agreed in Iraq's constitution has been held up for years. Arab and Turkmen minorities oppose the census because they say that Kurds, who have moved back to Kirkuk since 2003 en masse, have tipped the scales in their favour.
The Kurdish parliament passed a constitution last month defining all the disputed territories as Kurdish, a move U.S. Vice President Joe Biden on a visit described as "not helpful".
Though it simply restates the Kurds' position, the diplomat said the constitution was a swipe at Kirkuk's Arab and Turkmen.
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