BEIRUT -- Kurdish-led Syrian forces began an offensive Sunday to liberate the Islamic State militant group's unofficial capital, Raqqa, clashing with the extremists north of the Syrian city and warning neighboring Turkey not to interfere in the operation.
The United States, France and Britain said they would provide air support for the offensive, which was announced at a news conference by a coalition of Kurds and Arabs known as the Syria Democratic Forces. But it lacked details on how the group plans to oust the estimated 5,000 Islamic State fighters from the city.
The Raqqa offensive, which initially aims at isolating and encircling the city, increases the pressure on the Islamic State, making it harder for its fighters to move reinforcements between Syria and Iraq. The city, which has been under Islamic State control since early 2014, is home to some of the group's leaders and is seen as the key to defeating the group militarily.
The effort to isolate the city is the second of what U.S. military officials describe as roughly three phases in the operation to oust the militant group.
The first phase is what the U.S.-led coalition has been doing for months: conducting scores of preparatory airstrikes in and around Raqqa to knock out command-and-control and fighting positions as well as other assets of the Islamic State.
The third phase will be a fight for Raqqa itself, which U.S. officials say they hope will be conducted mostly by Syrian Arabs instead of the Kurdish-dominated forces, given that the city is majority Sunni Arab.
Senior commanders and representatives of the Syria Democratic Forces attended the news conference in Ein Issa, about 30 miles north of Raqqa. The Kurdish officials said the campaigns to oust the Islamic State from Raqqa and from Mosul, Iraq, are not coordinated but simply a matter of "good timing."
Cihan Ehmed, a militia fighter, said 30,000 fighters will take part in the offensive, dubbed Euphrates Rage, and that a joint operations command had been set up to coordinate various factions.
"I welcome today's announcement by the SDF that the operation to free Raqqa from ISIL's barbaric grip has begun," U.S. Defense Secretary Ashton Carter said, using an acronym for the Islamic State. "The effort to isolate and ultimately liberate Raqqa marks the next step in our coalition campaign plan."
Activists reported clashes Sunday between Islamic State militants and militia forces north of Raqqa.
Militia forces seized control of several villages and farms, the Britain-based Syrian Observatory for Human Rights said. It also reported strong activity by U.S.-led coalition warplanes and airstrikes that hit Islamic State positions. The Observatory said the Islamic State detonated two car bombs targeting the advancing forces.
The Raqqa-based Syrian activist group known as Raqqa is Being Slaughtered Silently also reported the clashes.
There was no immediate comment from the government of Syrian President Bashar Assad on the Kurdish announcement.
Brett McGurk, the White House envoy to the anti-Islamic State coalition, said the U.S. will provide air support for the Raqqa offensive and is in "close, close contact" with its ally Turkey. "We want this to be as coordinated as possible, recognizing that there will be a mix of forces on the field," he told reporters in Jordan.
A U.S. military spokesman in Baghdad, Col. John Dorrian, said U.S. warplanes are flying bombing missions on the Islamic State's "leadership, command and control and resources" in Raqqa and outside the city in support of the militia.
Britain said it is providing aerial surveillance to help in the offensive. The Royal Air Force "will support the Raqqa operation as it develops," Defense Secretary Michael Fallon said.
French Defense Minister Jean-Yves Le Drian said his country will provide airstrikes to aid the offensive. He told French radio network Europe 1 that "local territorial forces" should retake Raqqa with air support from the coalition but no foreign ground troops.
Dorrian said that "it may be some time" before the 30,000- to 40,000-strong force reaches Raqqa, and that the U.S.-led coalition will continue to train and recruit more forces -- especially Arab troops -- for an eventual attack on the city.
Coalition leaders have been struggling with the timing of the Raqqa campaign, not only because of the demands of the Iraqi-led Mosul operation but also because the political and military landscape in Syria is more complicated amid a civil war that has lasted more than five years and has devastated much of the country.
Political concerns
Unlike several successful efforts to drive Islamic State militants out of cities in Iraq, the Raqqa offensive faces several political obstacles.
In Iraq, the U.S.-led coalition is working with the government in Baghdad, but Washington and its partners in Syria are relying on a hodgepodge of local Arab and Kurdish opposition groups, some of which are fierce rivals. The tensions are exacerbated by Russian and Syrian forces on one side and by Turkish forces on another.
The Syria Democratic Forces is dominated by the main Syrian Kurdish fighting force known as the People's Protection Units. The U.S. considers the group to be the most effective force against the Islamic State, but Turkey views it as a terrorist organization linked to a Kurdish group outlawed by the government in Ankara. Turkish officials, including President Recep Tayyip Erdogan, have said they will not accept a role for the Kurds in the liberation of Raqqa.
In a speech Sunday, Erdogan did not comment on the announcement of the offensive but said allied Syrian opposition fighters were 9 miles from the Syrian town of al-Bab, the last stronghold of the Islamic State in Aleppo province. He added that Turkey's aim was to move on al-Bab and expel the militants toward the south.
"Our hope is that the Turkish state will not interfere in the internal affairs of Syria," Ehmed said at the news conference, suggesting the forces would defend themselves if it did. "Raqqa will be freed by its own sons."
Kurdish efforts to build an autonomous region in northern Syria have aggravated the country's sectarian politics -- with some U.S.-allied Syrian rebels opposed to the Kurdish moves -- and inflamed regional tensions.
Kurdish officials acknowledged their announcement was prompted by Turkey's growing assertiveness in northern Syria. Since August, Ankara has backed Syrian fighters opposed to the Kurds with tanks and aircraft and has bombed Kurdish forces.
The moves targeted Islamic State militants but also aimed at curbing Kurdish territorial ambitions in the country.
Information for this article was contributed by Zeina Karam, Philip Issa, Zeynep Bilginsoy, Karin Laub, Philippe Sotto and Gregory Katz of The Associated Press; by Eric Schmitt and Ceylan Yeginsu of The New York Times; and by Hugh Naylor and Zakaria Zakaria of The Washington Post.
A Section on 11/07/2016