Nikki Haley
© Carlos Barria / ReutersNut job Nikki Haley
The US will not be satisfied as long as Syrian President Bashar Assad is in power, US Ambassador to the UN said, commenting on a major de-escalation effort brokered by Russia, Iran and Turkey without American participation.

Russia, Turkey and Iran agreed Friday on the fourth, final, de-escalation zone in Syria, which is designed to ensure ceasefire between Syrian government forces and rebels for a period of six months in order to pave the way for a political resolution to the six-year war. The deal, which is also aimed at separating terrorist groups, including Islamic State terrorists (IS, formerly ISIS/ISIL or Daesh) and Jabhat al-Nusra (Al-Nusra Front) from so-called moderate opposition, was agreed with the approval of the Syrian government, as well as members of Syrian opposition who participated in the talks.

This came ten days after the Syrian army with Russia's help liberated one of Islamic State's last strongholds in Syria, the city of Deir ez-Zor, which had been under the terrorists' siege for three years. The lifting of the siege finally allowed humanitarian aid to reach the city.

"We're not going to be satisfied until we see a strong and stable Syria. And that is not with Assad in place," US Ambassador to the UN Nikki Haley said at a White House briefing on Friday, when asked whether the US was left behind in international efforts to resolve Syrian crisis.

American officials have said their main goal in Syria is to fight ISIS, as Washington backs the operations of Syrian Democratic Forces (SDF) which includes Kurdish fighters as well as Arab militia groups.

The SDF advanced towards Deir ez-Zor from the eastern side of the Euphrates river this week, in an effort to gain control of the city's eastern outskirts before the government does.

While Deir ez-Zor city was not an SDF target, the US-backed militias did not rule out the possibility that it may become one, saying people in the city wanted to be liberated from "the regime and Daesh at the same time," AP cited Abu Khawla, leader of the group advancing towards the newly liberated city.

On Thursday, the US-led coalition said the SDF was not planning to enter Deir ez-Zor city.

Abu Khawla told AP that the militia will not let Syrian government forces and their allies cross the Euphrates river to gain control of its eastern side.

Russian foreign ministry spokeswoman Maria Zakharova said Friday the Syrian army had already crossed.

"After a major victory near Deir al-Zor, the Syrian government army continues to clear Islamic State terrorists from the eastern regions of the country," according to Zakharova.

"The suburbs of this provincial centre have been liberated. Advance units have successfully crossed the Euphrates and are holding positions on its eastern bank," she added, without specifying the location.

On September 12, the Russian military said that the Syrian army had regained control of 85 percent of the country's territory.

The first UN humanitarian convoy arrived in Deir ez-Zor on Friday. Russia began delivery of aid to the embattled city last week, almost immediately after the siege was lifted.

"We fed our children with stale bread, cleaning the mold from it. We have long suffered from artillery strikes and shells; they usually hit civilians - children and women in particular," a local woman told RT, as residents described the horrors of life under siege.