The American-led coalition fighting the Islamic State has begun preparing to open a major front in northeastern Syria, aiming to put pressure on Raqqa, the terrorist group's de facto capital, according to military and administration officials. President Obama last week approved two important steps to set the offensive in motion over the coming weeks, officials said. Mr. Obama ordered the Pentagon, for the first time, to directly provide ammunition and perhaps some weapons to Syrian opposition forces on the ground. He also endorsed the idea for an increased air campaign from an air base in Turkey, although important details still need to be worked out. Together, these measures are intended to empower 3,000 to 5,000 Arab fighters who would join more than 20,000 Kurdish combatants in an offensive backed by dozens of coalition warplanes to pressure Raqqa, the Islamic State's main stronghold in Syria. Plans are also moving forward to have Syrian opposition fighters seal an important 60-mile part of the country's border with Turkey to cut off critical supply lines of the Islamic State, also known as ISIS. As recently as Friday, Mr. Obama said he would take all steps necessary to combat the Islamic State in Syria and Iraq. The new approach relies on Arab fighters whose commanders have been screened by American forces and Kurdish fighters who are more battle-tested and whose loyalties Washington can count on. "The top-line message that I want everybody to understand is, we are going to continue to go after ISIS," Mr. Obama told reporters. "We are going to continue to reach out to a moderate opposition." Senior administration officials say the new offensive holds promise and may change the dynamics on the ground. But it comes a year after an American-led coalition started a campaign against the Islamic State that is now "tactically stalemated," Gen. Martin E. Dempsey, then chairman of the Joint Chiefs, said last month. Whether the new approach can succeed remains to be seen. The Islamic State has proved to be more resilient to coalition attacks and adaptive in the face of international pressure than American officials anticipated — even managing to extend its reach and control in Syria and Iraq. The new American-led push would be conducted far from the brunt of the Russian air campaign in western Syria. That Russian operation has been directed largely at Syrian groups that oppose President Bashar al-Assad, and is only nominally aimed at the Islamic State, American officials said. The new northern front would be the opposite: It is entirely directed at weakening the Islamic State by trying to take away the group's home-court advantage, even as the militants hold on to Mosul and Ramadi in Iraq and Palmyra in Syria. These outlines of the mission have been drawn from public statements of senior commanders briefing Congress as well as interviews with more than a half-dozen military, diplomatic and administration officials who spoke on the condition of anonymity to discuss internal planning. Even in describing the goals of the campaign, officials said they would not disclose the kinds of details that might help the Islamic State anticipate exactly how the offensive would unfold. Gen. Lloyd J. Austin III, the commander of American forces in the Middle East, hinted at the emerging strategy last month, telling the Senate Armed Services Committee that over the next six months it would put "a lot more pressure on key areas in Syria, like the city of Raqqa." "Because of that access," General Austin continued, referring to the use of the air base in Turkey, "we'll have the ability to increase the pace and focus on key places in Syria. So that will certainly shake things in Iraq." Last Thursday, President Obama held a National Security Council meeting that endorsed the main elements of the strategy. At that meeting, administration officials said, Mr. Obama backed the basic idea for the Syrian Kurdish-Arab push toward Raqqa supported by United States and other coalition air power. On Wednesday, Secretary of State John Kerry alluded to the main elements of the northern front operation at a meeting at the United Nations Security Council. With the Russian foreign minister, Sergey V. Lavrov, presiding, Mr. Kerry said: "We are now in position with France, Australia, Canada, Turkey and other coalition partners joining the campaign, to dramatically accelerate our efforts. This is what we will do." Mr. Kerry said that "we will also be sustaining our support to anti-ISIS fighters in northeast Syria." "ISIS," he continued, "will soon face increasing pressure from multiple directions across the battlefield in Syria and Iraq." A spokeswoman for the National Security Council, Emily Horne, declined to comment on Sunday on the mission, citing "operational security." The origins of the northern front lie in the fight for Kobani, the Syrian Kurdish border city that faced an Islamic State onslaught last year. Kobani showed the potential for using a combined air and ground operation to defeat the Islamic State. The United States and its allies provided the combat aircraft, and Syrian Kurdish fighters, in contact with American Special Operations Forces in northern Iraq, provided the ground force. In just a few months, that campaign not only held onto Kobani, but also routed Islamic State fighters across a stretch of territory from the Euphrates River to the Iraqi border. The operation now being prepared would expand the Kurdish effort by adding Arab groups. In addition to increasing the number of anti-Islamic State fighters, the inclusion of Arab fighters eases Turkish concerns that the Syrian Kurds are becoming too influential in northern Syria. The Arab wing of this ground force is called the Syrian Arab Coalition, a conglomeration of 10 to 15 groups whose total numbers range from 3,000 to 5,000 fighters, American officials said. They would fight alongside a larger Kurdish force in the northeast of as many as 25,000 fighters. American military officials have screened the leaders of the Arab groups to ensure that they meet standards set by Congress when it approved $500 million last year for the Defense Department to train and equip moderate Syrian rebels. Most of the focus of that financing has been on an ill-fated Pentagon training program at sites in Turkey and Jordan that so far has fielded few fighters. The administration's plan is to support the Kurdish and Arab fighters and have them advance toward Raqqa, but not try to seize the heavily defended city itself. Rather, the aim is to isolate Raqqa and cut it off from travel and supply lines northeast and northwest of the city. Under planning for the northern offensive, coalition air power at the Incirlik air base in Turkey would also be expanded. More nations could base aircraft there. Australia, France and Turkey have all recently starting flying strike missions against targets in Syria. By gradually expanding the area of the coalition's air operations, the administration could protect more American-backed rebel forces and possibly hem in Russia's own operations, according to a European official and a senior American official. The administration's new plan, which was devised before the Russian buildup in Latakia, Syria, has not been coordinated with Russia, an administration official said, and the United States made it clear last week that its campaign against the Islamic State would not be thrown off course by the Russian strikes. But it seems likely that an effort will be made to "deconflict" American and coalition air operations in northern and eastern Syria from Russia's airstrikes once the new operation begins. Pentagon officials held a one-hour teleconference with their Russian counterparts on Thursday and presented a proposal for ways to minimize the risk of unintended confrontation. A follow-up discussion has yet to be held. In addition, the United States and Turkey continue detailed planning to use Arab militias to close a 60-mile stretch of border from the Euphrates River west to Kilis. The two countries reached agreement in late July on the basic concept, but now detailed planning is going forward on the assumption that Mr. Obama and President Recep Tayyip Erdogan of Turkey will bless it when it is done.
