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DAMASCUS, Syria — A defiant Bashar al-Assad expressed confidence that Syria’s bloody war could be won within months, saying Russia’s intervention has helped tip the scales toward victory.

Assad spoke exclusively to NBC News on Wednesday at his office in Damascus in a wide-ranging interview about the Syrian war, ISIS, the U.S. and his legacy.

He was unruffled by the State Department branding his vow to retake every inch of Syria as “delusional,” saying it was only a matter of time until he regained full control of his country.

Damaged buildings are pictured at a site hit by airstrikes in the rebel-controlled town of Ariha in Syria's Idlib province on Wednesday. AMMAR ABDULLAH / Reuters

“The Syrian army has made a lot of advancement recently,” Assad told NBC News. “It won’t take more than a few months.”

Assad's tone was strikingly different from a year earlier, when he was short of troops and losing territory to rebels and ISIS. The battlefield shifted, according to Assad, for one reason.

“The Russian support of the Syrian army has tipped the scales against the terrorists,” he said. “It was the crucial factor.”

His forces were teetering on the brink of defeat before Russia’s military intervention got underway in September. Since then, they've made significant territorial gains — like retaking the ancient city of Palmyra from ISIS.

While Russia has insisted its operations targeted terrorists, the West has accused Russian forces of bombing civilian targets and Assad's moderate enemies — not jihadis.

Russia's influence with Assad is in focus Thursday as Secretary of State John Kerry heads to Moscow for talks with Putin. Syria is high on the agenda — as is speculation of a backchannel deal involving Assad giving up power.

WATCH: NBC News' Full Interview with Syrian President

Assad however dismissed those rumors unequivocally, telling NBC News he was confident that Russia had his back.

“The Russian politics is not based on making deals — it's based on values,” he said.

And according to Assad, the “very frank” relationship he has with Putin is rooted in their shared values and common interest: defeating terrorists.

The Syrian president claimed that’s far from true of the U.S., which he accused of not truly wanting to see ISIS’ defeat.

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“They’re not serious,” Assad said.

He dismissed "illegal" U.S. airstrikes against ISIS in Syria as “counterproductive” and ineffective — compared to the “legal” firepower lent by Russia.

“The reality is telling that, since the beginning of the American airstrikes, the terrorism has been expanding and prevailing,” Assad explained. “It only shrinked when the Russians intervened.”

He attributed that to a lack of political will from the U.S. — and a different end goal.

“We wanted to defeat those terrorists, while the United States wanted to manage those groups in order to topple the government in Syria,” Assad said.

The U.S. demanded Assad’s ouster when civil war erupted in Syria. President Barack Obama in 2012 decscribed the use of chemical weapons as a "red line," then failed to act.

More than 250,000 people have died in the conflict, though the U.N. stopped keeping track of the toll. Efforts to negotiate peace have failed and cease-fires have broken down.

Six years later Assad is still in power and stronger than ever — but not crowing about outplaying Obama.

“He's failed, but that doesn't mean I win because for him the war is to remove me ... for me the war is to restore Syria,” he told NBC News. “If we can get rid of those terrorists, if we can restore the stability in Syria, this is where we win. Otherwise, you cannot talk about winning.”

“We always hope that the next president will be much wiser than the previous one"

With Obama nearing the end of his term, Assad will soon be confronting a new face in the White House. But that doesn’t mean the Syrian president expects much to change.

He accused successive U.S. administrations of stoking chaos around the world, “becoming more and more pyromaniac.”

Assad also was deeply skeptical — if not dismissive — of U.S. intentions in the region, saying American presidents have long lacked “credibility” in the Middle East.

“We always hope that the next president will be much wiser than the previous one ... That's what we hope, but we never saw,” Assad told NBC News.

He said the end of Obama’s term “means nothing” for Syria — and he’s not putting much stock in what has been said by presidential contenders thus far.

“In Syria, we never bet on any president coming or any president going,” he explained. “Cause what they say in their campaign is different from what they practice after they became elected.”

He told NBC News he has paid little attention to Hillary Clinton and Donald Trump’s campaigns, dismissing their words on the trail as “only rhetoric” for the time being.

“They're going to change after they become elected,” Assad explained. “And this is where you have to start evaluating the president — after the campaign.”

While Assad was ambivalent about who would be heading to the White House, he was unequivocal his own road ahead.

“When you are attacked by terrorists — I mean as a country — you have to defend your country, and that is my job according to the constitution,” he told NBC News. “So, I'm doing my job, and I'm going to keep doing it no matter what I'm going to face.”

That could mean one day facing an international war crimes tribunal — a prospect Assad said doesn’t faze him.

But he flatly rejects allegations he has committed atrocities, calmly questioning the validity of any evidence against him.

Using barrel bombs or chemical weapons? “No one has offered any evidence regarding this,” he said. “Only pictures on the internet.”

Children being killed? “Propaganda and media campaigns.”

Targeting civilians? “We didn't take any decision to attack any area that doesn't include terrorists.”

Widespread allegations his forces are using starvation as a weapon of war in sieges on rebel-held areas? “How do we prevent them from having food and we don't prevent them from having armaments to kill us ... This is not logic,” he laughed. “How could they survive for years if they are under besiege?"

That’s not to say Assad doesn’t acknowledge there have been victims in this war — but he sees himself as a patriot and his mission in black and white: Win the battle, by whatever means necessary.

“I defend my country,” he said, for the first time showing signs of agitation. “To talk about a clean war where there is no casualties, no civilians, no innocent people to be killed — that doesn't exist. No one could make it. No war in the world.”