US Defense Secretary Ash Carter(L) testifies to Senate Armed Services Committee during the hearing on national security and military operations on Capitol Hill in Washington DC, capital of the United States, Sept 22, 2016. [Photo/Xinhua]

WASHINGTON - Influential US Republican Senator John McCain on Thursday lashed out at President Barack Obama for his Middle East policy, describing it as "unmitigated disaster" that created a vacuum filled by terror groups.

McCain, chairman of the Senate Armed Services Committee, made the accusations in his opening remarks to the committee's hearing on national security and military operations, at which Defense Secretary Ash Carter and Chairman of Joint Chiefs of Staff Joseph Dunford testified.

The veteran senator said his committee has held such hearings regularly, with special attention paid to the chaos engulfing the Middle East and the US military campaign against the rising terror group Islamic State (IS).

"It will be up to future historians to render a final judgment on this administration's stewardship of US interests in the broader Middle East, but in the opinion of this one senator, it's been an unmitigated disaster," McCain said.

He criticized Obama for seeking to pivot away from Middle East, one of the most strategically vital regions of the world, out of a misplaced hope that "the tide of war was receding," and the US should focus on "nation-building at home."

The withdrawal of US forces from Iraq created a vacuum that was filled by "all of the worst actors" in the region, including Sunni terrorist groups such as Al-Qaida and IS, Iran and its proxies, and Russia, the senator claimed.

"Over the past eight years, this administration has overseen the collapse of regional order in the Middle East into a case of chaos where every country is a battlefield for regional conflict, a party to that conflict or both," he said.

The IS and Al-Qaida terrorist networks have expanded their influence from West Africa to South Asia and everything in between, McCain added.

He also criticized the Iranian nuclear deal that the Obama administration has touted as a diplomatic breakthrough in preventing Tehran from acquiring a nuclear bomb.

"The administration may have postponed Iran's nuclear programs, but this has come at the cost of unshackling Iranian power and ambition, both of which will grow in the coming years as billions of dollars in sanctions relief is transformed into advanced military capability and support for terrorism," he said, referring to the US easing of sanctions on Iran as part of implementing the nuclear deal.

McCain also pointed out that Russia has reclaimed a position of influence in the Middle East that is not enjoyed in four decades.

But the senator did commend Obama for sending US troops back to the region to fight IS militants. The military campaign is making progress though it is often "slow, reactive and excessively micromanaged by the White House," he said.

On Syria, McCain strongly criticized the Obama administration for failing to produce "a plausible vision of an end-state" for the country, where a protracted civil war has left more than 400,000 dead and half the population displaced, and created the worst refugee crisis in the century.

McCain attacked a recent truce deal reached in Syria brokered through the US-Russian partnership, saying "it would be deeply problematic, even if it were implemented."

This agreement would strengthen Syrian military position, "thereby undermining our own strategic objective of a political transition," he added.

Lindsey Graham, another Republican hawk, also blasted the Obama administration for lacking a coherent strategy for ending the Syria conflict.

He also described the US failure to establish a no-fly zone in Syria as a mistake.

In response to the criticism, Carter repeated three objectives of the US military campaign in the region, namely destroying IS, combating IS metastases everywhere they emerge around the world, and helping protect homeland security.

The US military has taken many steps to continually accelerate its campaign and the results of its effort are showing, though "we have much more work to do," the Pentagon chief said.

For his part, Dunford said he was encouraged by the progress being made in Iraq and Syria, and by the fact that the IS capabilities in Libya, West Africa and Afghanistan were degraded.

The top US military officer also made it clear that the US military did not intend to share intelligence with Russia in fighting IS.

At the same time, Dunford said he had "no doubt" that Russia is responsible for the airstrike on Monday that struck a humanitarian aid convoy in Syria, which killed 20 civilians.

Dunford said two Russian aircraft and Syrian military planes were in the airspace over Orum al-Kubra in Aleppo province when the airstrike took place. But he added that he was not sure which aircraft launched the strike.