Amman, Jordan ? Recent political gains by Iraqi Kurds are raising alarms in neighboring Turkey and increasing the risk of greater instability in Iraq’s oil-rich north.

The moves – among the most significant involving Kurds since the 2003 invasion of Iraq – have been largely overshadowed by the struggle to curb violence around Baghdad, but they could have a strong impact on Iraq’s future, including whether it remains a united country.

Kurdish boldness also comes at a critical time for Turkey, which is facing a growing threat in its own Kurdish region from separatist guerrillas raiding out of northern Iraq and has a presidential election coming up that could aggravate tensions between Islamist and secular Turks.

The fallout already has shaken relations between the United States and Turkey, a longtime ally increasingly frustrated that the overstretched American military in Iraq cannot crack down on Kurdish guerrillas.

That has the United States in a bind – “unwilling to open a new front in northern Iraq. Nor can it afford to lose its support from Iraq’s Kurdish population,” said Dr. Andrew McGregor, a security analyst and Kurdish expert in Canada, writing on the Web site of the Jamestown Foundation, a conservative think tank.

At the center of the fight are Kurdish aspirations for the ancient city of Kirkuk, the center of Iraq’s northern oilfields.

The Kurds want to incorporate Kirkuk into their self-governing region in northern Iraq. They won a major concession in March when they pressured the government of Iraqi Prime Minister Nouri al-Maliki into approving plans to move thousands of Arabs out of Kirkuk and resettle them elsewhere.

The program targets Arabs who moved to Kirkuk after July 14, 1968, when Saddam Hussein’s party took power. Saddam sent thousands of Arabs, many of them impoverished Shiite Muslims from the south, into Kirkuk to dilute the Kurdish presence there.

The Kurds’ aim is to reduce the Arab population of the city before Kirkuk residents vote later this year whether to join the Kurdish self-governing region.

Opponents hope to delay the referendum or cancel it altogether. They fear that gaining control of Kirkuk would lead the Kurds, who make up 15 percent to 20 percent of Iraq’s population, to set up an independent country entirely.

Nevertheless, the opponents within al-Maliki’s administration caved in after the Kurds threatened to resign from the Cabinet – a move that would have spelled the end of the fragile, U.S.-backed governing coalition.

The Kurds used similar hardball tactics in February to win concessions granting them a major say in what companies are granted rights to exploit Iraqi oilfields in Kurdish-controlled areas.

But the March decision on relocation was even bigger, sending shock waves into neighboring Turkey, which has long feared the rising stature of Iraqi Kurds will further embolden Kurdish guerrillas fighting for self-rule in southeastern Turkey.

The insurgent Kurdistan Workers Party, or PKK, use bases in northern Iraq to launch attacks into southern Turkey, and Turkey is growing angry over the failure of U.S. and Iraqi forces to curb the attacks.