BEIRUT (AP) — Syria's Kurds on Thursday declared a de-facto federal region in Kurdish-controlled areas of northern Syria, drawing sharp condemnation from both the Damascus government and its opponents who decried the unilateral move as unconstitutional and setting a dangerous precedent.

The declaration further complicates the situation on the ground in Syria even as peace talks press ahead in Geneva. The main Syrian Kurdish party has been excluded from those talks — perhaps an indication of why the Kurds chose this particular moment for their move.

In Syria's civil war, Kurdish fighters have emerged as the most effective fighting force against the Islamic State group and are backed militarily by the United States. More recently, Russia has backed them politically.

But despite Russia's insistence that they should be part of the talks that started this week in Geneva, they have not been invited because Turkey considers the group to be a terrorist organization.

"Everybody rhetorically appreciates the Kurds, they all acknowledge the Kurdish fight against ISIS and that they are great warriors, but this is not being reflected in the diplomatic spectrum," said Mutlu Civiroglu, a Washington-based Kurdish affairs analyst, using an alternative acronym for the Islamic State group.

Thursday's announcement triggered fears that a Kurdish federal unit would lead to a partition of the war-shattered country — a formula that may make sense in principle after five years of devastating fighting but one that would be messy and unpalatable to most parties.

Some 200 Kurdish officials, who met in the town of Rmeilan in Syria's predominantly Kurdish province of Hassakeh, insisted they are not partitioning Syria nor seeking secession — but rather making sure the country remains one nation.

"A federal and democratic Syria is a guarantee of coexistence and brotherly relations," said an online posting from the conference.

Nawaf Khalil, an official with the Democratic Union Party, or PYD, said participants at the Rmeilan meeting included Turkmen, Arabs, Christian and Kurds.

They all approved a "democratic federal system for Rojava-Northern Syria," he said. Rojava is a Kurdish word that refers to three distinct enclaves, or cantons, under Kurdish control in northern Syria: Jazira, Kobani and Afrin.

The Kurds, a longtime oppressed minority under decades of Assad family rule, have taken advantage of the chaos of the civil war to advance their goals of autonomy. After overstretched government troops withdrew from Kurdish areas to focus on fighting insurgents in other parts of the country, they declared their own civil administration in those three areas in 2013.

It was not immediately clear how the declaration of a federal region would change the situation on the ground.

"The idea of a decentralized Syria is becoming every day more and more common," said Civiroglu, the analyst. "I see that it can be a real system for all of Syria in the future, something tried on the ground."

Syria's Foreign Ministry rejected the move, describing it as "unconstitutional and worthless" and warned against any attempt to encroach upon the integrity of Syrian territory.

The Syrian National Coalition, one of the main Syrian opposition groups, also said it rejects such unilateral declarations and warned of any attempt to form autonomous regions that "confiscate the will of the Syrian people."

The idea of a federal region appears to have gained some traction lately as world and regional powers grapple with ways to end the conflict.

Russian Foreign Minister Sergey Lavrov this week said a federal system is one possible option if the Syrian people agree to it. The United States has also been an ardent supporter of the Kurds in Syria and in the wider region but has not commented on Thursday's declaration. Turkey said Wednesday that such unilateral moves carry no validity, but did not comment Thursday.

The plan could make sense in a country that has a multitude of sectarian and ethnic minorities for whom it would be difficult to share a unifying national sentiment.

But Syria's war, with its changing front lines, has also created a geographical chaos.

The government, dominated by President Bashar Assad's Alawite sect of Shiite Islam, controls Damascus, the Alawite heartland along the Mediterranean coast, and other cities and connecting corridors in between. The Kurds run their own affairs in the northeast.

The militants of the Islamic State group control much of the Sunni heartland in the east. Other Sunni rebels control pockets in the north and south. Members of the Muslim minority Druse, who make up about 5 percent of Syria's prewar population of 23 million, have also started talking about autonomy in their southern areas.

But any move to carve up the country could risk yet more violence, including ethnic or sectarian cleansing.

Kurds control an area along the Turkish border stretching from eastern Syria, near the Iraqi border, to Afrin in the west, interrupted only by a stretch of territory controlled by the Islamic State group.

"Only a Kurdish federal region is definitively possible since the Kurds control most of their territories in Kobani and the Hassakeh province," said Wladimir van Wilgenburg, a political analyst with Jamestown Foundation specializing in Kurdish politics.

"The only problem they have is that they have not connected nor linked their administrations from Kobani up to Afrin," he added.

Meanwhile, the U.N. envoy for Syria emerged from the fourth day of peace talks in Geneva to tell reporters that significant gaps remain between the two sides.

Staffan de Mistura said he'd host both sides separately on Friday to accelerate the process. He said there were "no discussions about federalism" — a reference to the Syrian Kurdish declaration.

In other developments, 61 trucks with aid from the International Committee of the Red Cross and the United Nations began entering four areas besieged by government forces and insurgents, said ICRC spokesman Pawel Krzysiek.

The U.N. Office for the Coordination of Humanitarian Affairs, or OCHA, said on its Twitter account that aid is on the way to the rebel-held towns of Madaya Zabadani, near the border with Lebanon, and the government-held villages of Foua and Kfarya in the northwestern Idlib province.

A U.N. aid official, Jan Egeland, said the world body has given the Syrian government its plan to deliver humanitarian aid to 1.1 million Syrians by the end of April. But he said Damascus still has not granted authorization for aid to six of 18 priority areas the U.N. hopes to reach.

From Moscow, Vladimir Putin warned that despite the Russian drawdown in Syria — a surprising move the Russian president announced this week to bolster the Geneva talks — Russia can again build up its forces "in a few hours" in the Mideast country if necessary.

Putin said that Russia has kept some forces in Syria to support the Syrian army's action against militant groups and would continue striking them.

The statement underlined Russia's intention to maintain a strong military presence in Syria to keep its gains after a five-and-a-half-month air campaign that has helped turn the tide of war and allowed Assad's forces to make significant advances.

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Associated Press Writers Vladimir Isachenkov in Moscow, Jamey Keaten in Geneva and Bassem Mroue in Beirut contributed to this report.