Defeat of ISIS only a matter of time: US

The defeat of the ISIS in Syria is only a matter of time, but there is a need for a security situation that is conducive to reconstruction in the war-torn country, a top US official said today.

US national security adviser H R McMaster said the forces who will take over after the defeat of ISIS will be critical for establishing security and legitimacy of the population in the country.

“It is a matter of time only until ISIS is defeated there (in Syria),” said McMaster, who is currently in Afghanistan.

“What's going to be really critical though is what forces can then establish enduring security in those regions that have a legitimacy with the population, that are representative of the population, that can set conditions for reconstruction to begin,” he told ABC News in an interview.

McMaster said the US was now supporting partner forces in Syria in certain parts of the country, including the northeastern part along the Euphrates river valley.

"The cities of the Sunni Arab world in that region are in rubble. And so in a very successful conference in Washington two weeks ago, the United States State Department organised a bunch of donors and like-minded allies, part of coalition to pledge money for reconstruction," he said.

"But what we need now is we need a security situation that's conducive to that reconstruction, that can allow so many of these displaced people and refugees to return. And for those long-suffering people to enjoy the security, stability, that they deserve,? McMaster said.

War in Syria has killed more than 320,000 people since it began with protests in 2011 that were brutally repressed.

It has involved jihadist groups as well as regional and international powers in a complex multi-sided conflict.

The fighting has caused millions to flee their homes and triggered a major humanitarian and refugee crisis.