The Kurdistan Democratic Party (KDP) said it would not take part in the June 10 vote following a February ruling by the Federal Supreme Court to amend the electoral law.

That decision reduced the number of seats in the Kurdish parliament from 111 to 100, effectively eliminating a quota reserved for Turkmen, Armenian and Christian minorities.

It also ruled that the Iraqi Electoral Commission should oversee the vote instead of local committees.

"We believe that it is in the interest of our people for our party not to comply with an unconstitutional decision and a system imposed from the outside," the KDP said in a statement.

The KDP will not take part in a vote "imposed" by the court that "violates the law and the constitution", it added.

The KDP is the largest party in the outgoing Kurdish parliament with 45 seats.

It is followed by the Patriotic Union of Kurdistan (PUK) which has 21 seats and enjoys friendlier ties with the federal government in Baghdad.

Under a tacit agreement between the two parties, a PUK member holds the Iraqi presidency, which is reserved for a Kurd, while the president of the Kurdish region is selected from the KDP.

A boycott of local polls by the KDP might further delay the election which had been originally slated to take place on October 22.

Last week, Christian and Turkmen political parties also announced plans to boycott the vote.

The United States, a key supporter of Iraqi Kurdistan, said it was "concerned" by the KDP decision and called for "full participation in free, fair, transparent and credible elections" .

"We also understand many of the concerns raised by Iraqi Kurds with respect to recent decisions made by the federal institutions," State Department spokesman Vedant Patel told reporters in Washington.

But he added, "we don't think that boycotting these elections will serve the interests" of Kurds or Iraqis more broadly.

The Kurdistan region has been autonomous since 1991.

Relations with Baghdad have long been tense mainly over funds allocated by federal authorities to the Kurdistan region and revenues from its large oil wealth.