U.S. Defense Secretary Ash Carter urged Turkey on Tuesday to do more to help destroy Islamic State militants as he kicked off a tour of the Middle East that aims to drum up regional support for the military campaign.
Speaking to reporters while traveling to the Incirlik air base in southern Turkey, Carter said Ankara needed to better control its border with Syria, particularly a roughly 60-mile (98-km) stretch believed to be used by Islamic State for illicit trade and for shuttling foreign fighters back and forth.
"Turkey has an enormous role to play," said Carter, on his first trip to Incirlik as defense secretary. "We appreciate what they're doing. We want them to do more."
That includes Turkish forces joining "in the air and the ground as appropriate," Carter said. "The single most important contribution that their geography makes necessary is the control of their own border."
Incirlik has grown more important in the U.S.-led campaign of air strikes against Islamic State, with 59 U.S., Turkish, Qatari and German aircraft conducting refueling, intelligence, and strike missions now operating out of the base, up from about 15 from all coalition countries at the beginning of September, U.S. officials said.
That number is expected to increase in the coming weeks and months, though officials did not provide details.
Around 45 of the 59 aircraft using Incirlik are from the United States and include both manned and unmanned.
The United States has pushed for a more assertive Turkish contribution in fighting the Islamic State, particularly in securing the border with Syria, but also in seeing more Turkish air strikes devoted to Islamic State.
On Monday, speaking after a meeting of the U.S. National Security Council at the Pentagon, President Barack Obama said Carter's trip to the region aimed to secure greater military contributions from allies in the campaign against Islamic State.
Carter's visit to Incirlik comes amid increased tensions between Turkey and Iraq over the deployment of Turkish troops this month to a base near the northern Iraqi city of Mosul. Baghdad has appealed to the United Nations Security Council to demand the troops' withdrawal, while Turkey says the troops are part of an international mission to train and equip Iraqi forces to fight Islamic State.
On Monday, Turkish troops started leaving their camp in Iraq and moving north.
At Incirlik, where the number of U.S. personnel has increased to 1,300 from around 300 in July, Carter was due to speak to U.S. military officials and to hold a 'town hall' meeting with family members of U.S. troops.
Carter says he has written to allies to suggest additional contributions to the campaign against Islamic State. He did not give details of the requests but said different countries' contributions could include strike aircraft, intelligence flights, transport aircraft, help in controlling borders and helping U.S. efforts to train troops.
On Tuesday, Saudi Arabia announced the formation of a 34-nation Muslim military coalition to combat terrorism.
Carter said Sunni Gulf Arab countries could encourage and help Sunni Muslim communities living in areas controlled by Islamic State, a hardline Sunni group, to resist their rule.
"That's something that obviously they can do that it's harder for other countries to do," he said.
"Different countries can make different kinds of contributions and over this trip and in the subsequent weeks and months I'll be asking them each to make the strongest, most robust possible contribution that they can."