Washington (AFP) - The Pentagon under President Donald Trump is enjoying greater freedom to run its wars the way it wants -- and not constantly seek White House approval on important decisions.

Many in the military appreciate this increased autonomy, but critics charge it is raising civilian death rates, puts the lives of US troops at greater risk and leads to a lack of oversight of America's conflicts.

Nowhere has the shift been more visible than in the fight against the Islamic State group in northern Syria, where under Barack Obama even minor tweaks to US plans underwent exhaustive White House scrutiny.

Since Trump's inauguration, the Marine Corps has brought an artillery battery into Syria, and the Army has moved in hundreds of Rangers, bringing the total number of US forces there to almost 1,000.

Commanders are weighing the possibility of deploying hundreds more, and the Pentagon this week announced it had provided artillery support and choppered local forces behind enemy lines in a bid to seize a strategic dam.

The greater leeway marks a departure for the National Security Council (NSC), which coordinates foreign and military policy and implements the president's national security agenda.

Under Obama, the NSC oversaw just about every aspect of America's wars in Iraq, Syria and Afghanistan, with then Pentagon chief Ash Carter was kept on a short leash.

Trump, conversely, has repeatedly deferred to his defense secretary, Jim Mattis, on military moves.

Mattis, a retired general, has delegated expanded authorities to his battlefield commanders.

"Jim Mattis has been given the latitude to conduct military operations in the way he sees best," Pentagon spokesman Chris Sherwood said.

- '30-something year olds' -

The United States is fighting IS in Iraq and Syria and the Taliban in Afghanistan "by, with and through" local forces backed by US and allied air power.

That overall strategy hasn't changed, but commanders now have greater discretion to move troops and equipment around.

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Troop increases were especially sensitive for Obama, who campaigned on a promise to end America's Middle East wars and not put US boots on the ground.

Senator John McCain, who heads the Senate Armed Services Committee, was a frequent critic of what he calls NSC micromanagement.

The veteran lawmaker said he favors battlefield commanders getting greater latitude.

"We don't have to ask the 30-something-year-olds for permission to respond to an attack in Afghanistan," he said.

McCain's congressional counterpart Mac Thornberry described a visit he made to Afghanistan under Obama, when he overheard a call from an NSC staffer asking how much fuel was in the planes on the tarmac.

"The level of micromanagement was incredible, and of course by the time you work your way through the NSC process your target has moved," he said.

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- Hands off -

Trump has also faced criticism for his hands-off approach, especially after he approved a special operations raid in Yemen that went horribly wrong, leading to the death of a Navy SEAL, multiple civilians including children and a crashed helicopter.

Though the White House insisted the raid yielded vital intelligence and was a "successful operation by all standards," critics said the military had been rash to execute the mission.

Observers are also calling into question whether the Pentagon is allowing civilian casualties to mount.

Military officials vehemently deny this and stress that civilian safety is a top priority in approving any strike.

Airwars, a London-based collective of journalists and researchers, said Friday it had become so overwhelmed tracking civilian deaths allegedly caused by US and coalition planes that it has stopped tracking Russian strikes.

"The decision to temporarily suspend our Russia strike assessments has been a very difficult one to take," Airwars director Chris Woods said.

"Moscow is still reportedly killing hundreds of civilians in Syria every month. But with coalition casualty claims escalating so steeply -- and with very limited Airwars resources -– we believe our key focus at present needs to be on the US-led alliance."

The Pentagon has acknowledged at least 220 civilians have been unintentionally killed since operations to defeat IS began in late summer 2014. Airwars estimates the real number to be more than 10 times that.

The Syrian Observatory for Human Rights monitoring group said a coalition air strike early Tuesday killed 33 displaced civilians near the town of Al-Mansura west of Raqa.

A US defense official stressed that any extra deaths are a result of fighting occurring in more densely packed urban areas, such as Mosul in Iraq and around Raqa in Syria.

"I know for a fact that there is no change in civilian casualties tolerance," the official said.

General Thomas Waldhauser, who heads the US Africa Command, said Friday he hopes the White House will loosen restrictions for operations in Somalia, where the US is targeting Shebaab militants.

"It allows us to prosecute targets in a more rapid fashion," he said, stressing new authorities would not come at the expense of civilians.

"The cardinal rule in these types of engagements is to not make more enemies than you already have," Waldhauser said.

"We are not going to turn Somalia into a free-fire zone."