REUTERS - The United States' new envoy to the coalition it leads against the Islamic State said on Wednesday its priority was to seal the last strip of border between Turkey and territory held by the ultra-hardline group in Syria.
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The United States and Turkey have for months been talking of a joint operation to clear ISIS from the remaining part of the frontier but there has been no sign of progress.
"We are increasing our pressure there," said Brett McGurk, without elaborating.
The aim is to deprive Islamic State of a smuggling route that has swollen its ranks with foreign fighters and filled its coffers with illicit trade.
The effort comes at a time when Turkey and the U.S.-led coalition of which it is part find themselves increasingly at odds with Russia as it becomes more involved in the conflict in both Syria and Iraq.
McGurk, who was appointed by U.S. President Barack Obama in October, said that only 30 percent of air strikes conducted by Russia in Syria targeted Islamic State and the rest hit "other armed groups".
"Our air campaign in Syria, we think it's very effective and we have the data to back that up. The Russian air campaign has different objectives quite frankly," he said at a briefing for the media in Baghdad.
Russia launched air strikes in Syria at the end of September in support of its ally, President Bashar Assad, with the stated aim of hitting Islamic State.
The West has accused Moscow of mostly targeting Western-backed rebel groups fighting Assad, and a Reuters analysis of Russian Defense Ministry data in October showed almost 80 percent of Russia's declared targets in Syria had been in areas not held by Islamic State.
The intervention of Russia, which is allied with Iran, has added a new degree of complexity to a conflict that has already drawn in most of the world's major powers.
Turkey shot down a Russian jet that it said strayed into its airspace last month, an allegation Moscow denies.
Last week, Turkey deployed a contingent of troops to a base in northern Iraq, provoking an outcry in Baghdad, which condemned it as a violation of Iraq's sovereignty.
McGurk said the deployment had not been carried out within the framework of the coalition and hoped Baghdad and Ankara would resolve the dispute diplomatically.
Despite the differences between the forces arrayed against Islamic State, McGurk said the militants were feeling the heat.
"Daesh is no longer an organization where it can mass forces in one area to mount major offensive operations," he said using an Arabic acronym to refer to the group. "It has to do multiple things at once. This makes them think twice and they make stupid mistakes which enable us to find their leaders and kill them".