BAGHDAD  With little notice and almost no public debate, Iraq’s Kurdish leaders are pushing ahead with a new constitution for their semiautonomous region, a step that has alarmed Iraqi and American officials who fear that the move poses a new threat to the country’s unity.

The new constitution, approved by Kurdistan’s parliament two weeks ago and scheduled for a referendum this year, underscores the level of mistrust and bad faith between the region and the central government in Baghdad. And it raises the question of whether a peaceful resolution of disputes between the two is possible, despite intensive cajoling by the United States.

The proposed constitution enshrines Kurdish claims to territories and the oil and gas beneath them. But these claims are disputed by both the federal government in Baghdad and ethnic groups on the ground, and were supposed to be resolved in talks begun quietly last month between the Iraqi and Kurdish governments, sponsored by the United Nations and backed by the United States. Instead, the Kurdish parliament pushed ahead and passed the constitution, partly as a message that it would resist pressure from the American and Iraqi governments to make concessions.

The disputed areas, in northern Iraq, are already volatile: There have been several tense confrontations between Kurdish and federal security forces, as well as frequent attacks aimed at inflaming sectarian and ethnic passions there.