Helicoptering across northern Iraq for high-profile visits to the region's top two Kurdish leaders, Deputy Defense Secretary Paul D. Wolfowitz voiced strong support Thursday for protecting minority rights for ethnic Kurds in a new Iraqi political structure but also urged Kurds to resist secessionist notions and work for a united national government.

The separate meetings with Kurdish leaders Massoud Barzani and Jalai Talabani underscored U.S. interest in promoting accord among Iraq's Shiite Arab, Sunni Arab and Kurdish communities to ensure the emergence of a unified, democratic nation.

Earlier this month, Barzani and Talabani threatened to distance their Kurdish parties from the Iraqi state and possibly secede altogether. They were upset over the absence of any mention of Iraq's interim constitution in a U.N. resolution adopted June 8 that affirmed the planned transfer of Iraqi sovereignty June 30.

The interim constitution, hammered out in March, offered the Kurds some protection by essentially granting them a veto over ratification of a permanent constitution. It did this by stipulating that if two-thirds of voters in three of the country's 18 provinces rejected the constitution, it would not be adopted. There are three provinces with a Kurdish majority. Iraq's interim prime minister, Ayad Allawi, pledged last week that his government would adhere to the interim constitution until elections next year. But what happens after that remains in doubt, and tensions over the issue have highlighted the challenges ahead in crafting arrangements that will balance Iraq's main political, religious and ethnic groups.

"We Americans think it is very important that Kurds should be first-class citizens in their own country," Wolfowitz told reporters after a luncheon meeting with Barzani at a guest house outside the city of Irbil. "It's important because an Iraqi government that treats its Kurds as first-class citizens will treat all its people as first-class citizens."

Barzani welcomed Wolfowitz's visit, calling it reassuring and adding that it reflected the "importance and care" with which the United States has handled Kurdish issues.

Later, a dinner meeting between Wolfowitz and Talabani in this lake area in northeastern Iraq, yielded a renewed public commitment from the other Kurdish leader to pursue a unified national government.

In remarks to reporters afterward, Wolfowitz offered what he described as a new, more positive reason for opposing Kurdish secession than the traditional argument that a unified Iraq is important for regional stability.

"The unity of Iraq is important also because Kurds, with their general outlook and with their 12 years of experience of real self-government, have something enormously important to contribute to a free and democratic Iraq," he said.

The Kurds operated an autonomous region of northern Iraq after the 1991 Persian Gulf War, protected by U.S. and British air patrols. Now, the Kurds worry about losing the U.S. protection and falling subject to a government in Baghdad ruled by Iraq's Shiite majority.

Kurds are represented prominently in the interim government formed earlier this month, filling both a vice presidency and a deputy premiership, although Wolfowitz noted that Kurdish leaders had hoped to get one of the top two posts, prime minister or president.

Also, when the new Iraqi government and U.S. occupation authorities moved last week to declare all militia groups illegal, the two main Kurdish organizations -- the Kurdistan Democratic Party and the Patriotic Union of Kurdistan -- won special provisions. Many Kurdish fighters, known as pesh merga, will be allowed to form specialized units under the command of the Kurdish regional government that controls northern Iraq.

Deputy Defense Secretary Paul D. Wolfowitz, center, gives a gift pen to provincial governor Usama Kashmula at the U.S. military-controlled airport in Mosul, Iraq.