The United States, Russia, France, and the United Kingdom "have actively added fuel to the fire of the Syria conflict."

That's the charge from 30 humanitarian groups including Oxfam, the Norwegian Refugee Council, Save the Children, and the Syrian-American Medical Society in a report (pdf) released Friday that looks at the failures of these members of the UN Security Council and the International Syria Support Group in helping to bring an end to ongoing civilian suffering.

This month marks the fifth year of the conflict in Syria in which at least 250,000 people have been killed, according to UN estimates. Before the conflict broke out, the average life expectancy was 70.5 years. But in 2015, that figured dropped to 55.4. Poverty has also soared, jumping from 35 percent to 85 percent, while immunization coverage has fallen from 90 percent to less than 60 percent.

And during the past year, the report says, "the suffering has only worsened."

"The Syrian government and its allies, as well as armed opposition and extremist groups, bear the primary and direct responsibility for the horrific reality Syria's civilians face on this grim anniversary," the report states, yet these four nations, "which should play a key role in ending the suffering in Syria—are actively contributing to that very suffering."

They're doing that by flouting their own UN Security Council resolutions, implementing inadequate diplomatic pressure, and by pursing a military strategy "with varying degrees of direct consequences for the civilian population and escalation of the conflict."

The U.S. in 2015, for example, "spent $11.5 million a day on its bombing raids in Syria and Iraq. The U.S. also directly transfers weapons to armed groups inside Syria." There have been reports of "damaged civilian infrastructure and nearly 300 civilian casualties," the report says. That's despite Security Council resolutions demanding all parties end stop "indiscriminate use of weapons, including through shelling and aerial bombardment" that can result in civilian casualties.

And Russian bombing raids have, despite goals of Security Council resolutions, been barriers to access to humanitarian assistance.

"The last year was the most miserable yet for Syrians," stated Mark Goldring, Chief Executive of Oxfam GB.

"While the failure to end the terrible violence must primarily rest with those involved in the fighting, their international backers also have a responsibility to safeguard hope rather than fuel the fire. They have to decide whether they are committed to ending this catastrophe or to continuing its escalation. We have seen the impact of airstrikes, now it is time to see the impact of diplomatic pressure in bringing peace to Syria," he said.

The new report comes just ahead of a round of UN-mediated peace talks set to begin Monday.