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The US and Russian militaries have agreed to resume communications aimed at preventing mid-air collisions over Syria as a Moscow-sponsored "de-escalation plan" comes into force.

However, despite enhanced cooperation, confusion remains over logistics governing the plan aimed at stymying violence in the country, and bringing about an end to more than six years of brutal conflict that has left hundreds of thousands dead, and forced millions from their homes.

The de-escalation plan for Syria came into place on Friday.

An end to bloodshed?

The deal brokered by regime backers Russia and Iran - as well as rebel supporters Turkey - was signed during peace talks in the Kazakh capital Astana last week.

It calls for the establishment of four "de-escalation" zones across stretches of eight Syrian provinces.

US President Donald Trump has also called for the establishment of "safe-zones" inside Syria on a number of occasion since taking office.

The agreement seeks to ground all military aviation in the four areas, including flights by the US-led coalition fighting the Islamic State group.

Under the plan Russian combat planes are set to be able to strike IS areas, mostly in eastern Syria, which are outside the designated safe zones.

Russian-US cooperation

Over the weekend, phone discussions between Russian General Valery Gerasimov and US General Joseph Dunford led to the re-establishment of an aircraft safety memorandum for Syria between the two global powers.

That agreement was signed by Washington and Moscow in October 2015 after Russia began its military campaigns in the country in support of the Assad regime.

However, it was reportedly suspended by Moscow after the Trump administration ordered an airstrike on a Syrian regime airbase in April.

The US cruise missile attack was intended as a warning to the Syrian regime after it was deemed responsible by Washington for carrying out a chemical attack on rebel-held territory.

Both the Syrian regime and its Russian backers deny responsibility for the attack which targeted the town of Khan Sheikhun in Idlib province.

While the US, the UN, and Saudi Arabia have expressed support for the deal, opposition figures have objections.

Some rebel group have expressed anger at the position of Iran - which has poured thousands of troops into the country to prop up the Assad regime - as a guarantor to the agreement.

Washington's lingering scepticism

In the aftermath of the "safe zones" implementation on Friday, figures within the US military establishment also expressed some scepticism towards the deal, and in particular questioned the banning of US aircraft from operating over these safe zones.

Such scepticism regarding the efficacy of the plan was re-iterated this week by US Defence Secretary James Mattis.

Speaking on Monday, Mattis said that while the safe-zone plan had come into place, and had Washington's backing, logistic details concerning its ongoing implementation remained unresolved, and a work in progress.

Reports have suggested that, under the deal, security cordons on the edges of the established safe-zones would be established to monitor and ensure access, with forces from the three guarantor nations manning checkpoints and observation posts.

However, precise details of the plan remain unclear.

Confusion over logistics

Syrian Foreign Minister Walid Muallem has notably expressed objection to the UN playing any role in the implementation and monitoring of the agreement.

"It's not been decided, in the sense that these are the specific safe zones, here's who's going to be ensuring they're safe, who is signing up for it, who is specifically to be kept out of them.

"All these details are to be worked out and we're engaged," said Mattis, speaking in Copenhagen on Monday ahead of an anti-IS coalition meeting.

"The devil's always is in the detail."

Despite, tentative backing for the Russian plan, figures within the US administration also remain sceptical that the Assad regime will refrain from violating its terms.

Numerous previous ceasefire deals for Syria have fallen by the wayside, amid mutual accusations from regime and rebel groups, of violations.

Minor violations of the latest agreement have been reported since its implementation on Friday, according to opposition activists. 

A US State Department statement released last week said that "in light of the failures of past agreements, we have reason to be cautious.

"We expect the regime to stop all attacks on civilians and opposition forces, something they have never done. We expect Russia to ensure regime compliance," said the statement.

Syria has been embroiled in fighting since 2011 when anti-government protests were brutally put down by regime forces sparking a larger armed uprising.

The fighting has cost Syria nearly 500,000 lives, the vast majority victims of regime bombing.