President Barack Obama has said the US is not putting its troops on the front lines in Syria to fight the Islamic State of Iraq and the Levant (ISIL), despite his decision to deploy special operations troops on the ground.

In his first comments since the deployment was announced on Friday, Obama said it was merely an extension of what the US was already doing.

"Keep in mind that we have run special ops already and really this is just an extension of what we are continuing to do," Obama said in an interview on NBC Nightly News on Monday.

"We are not putting US troops on the front lines fighting firefights with ISIL," Obama said.

"I have been consistent throughout that we are not going to be fighting like we did in Iraq with battalions and occupations. That doesn't solve the problem."

Train, advise and assist

In announcing the measure, the White House said the troops would be on a mission to "train, advise and assist" and would number fewer than 50.

The introduction of US forces on the ground marks a shift after more than a year of limiting the Syria mission to air strikes against ISIL.

Before last year, Obama, who has been averse to committing troops to Middle East wars, had ruled out a US presence on the ground in Syria.

In a nationally televised address in September 2013, Obama said: "I will not put American boots on the ground in Syria."

Over the past year, however, he has emphasised that he would not send US "combat" troops there.

The Obama administration is under pressure to ramp up the US effort against ISIL, particularly after the group captured the Iraqi city of Ramadi in May and following the failure of a US military programme to train and arm thousands of Syrian rebels.

Russia and Iran have increased their military support for Syrian President Bashar al-Assad's fight against rebels in the civil war, now in its fourth year.

American soldiers have begun training units of Niger's army at the edge of the Sahara Desert, in what a U.S. official calls a “new wave” of military support for African states battling Boko Haram militants.

More training will follow for national armies in Cameroon, Nigeria and Chad, the official told VOA, speaking on condition of anonymity. Extremists from Boko Haram are based in northeastern Nigeria, but they have carried out notorious attacks throughout the Lake Chad region - Niger, Chad, Cameroon and Nigeria.

Training in Niger began on October 19 at Agadez, the largest city in central Niger, once a center for caravans crossing the Sahara.

The Niamey government requested the U.S. mission to Niger, U.S. Africa Command spokesman Chuck Prichard told VOA Wednesday.

About 40 American soldiers who arrived last week at Niger-controlled Air Base 201 will provide eight weeks of training to about 150 Nigerien troops. Prichard said instruction will cover basic soldier skills, including small-arms marksmanship.

"This training benefits Nigerien military personnel and U.S. Army soldiers who share the mutual security goal of regional stability and security in Africa," said Major General Daryl Williams, the commander of U.S. Army Africa.

The U.S. embassy in Niger says the training program is expected to last a few months, with a goal of enhancing “the professional skills of the Nigerien military personnel with an emphasis on airfield security procedures."

The Pentagon says Master Sgt. Joshua Wheeler, the Delta Force soldier who died last week in a hostage rescue mission in Iraq, was the first U.S. service member killed in action in the ISIS war. But Wheeler was not the first combat casualty.

Five other service members have been “wounded in action” since the U.S. first sent troops back into Iraq last year, according to statistics from the Pentagon and interviews with officials in Iraq (PDF). But how and when they were injured, the Pentagon refuses to say.

As the Obama administration holds to the increasingly dubious claim that U.S. troops are not engaged in combat against the self-proclaimed Islamic State, the Pentagon is withholding details about its wounded that would give key insights into the kind of fight American troops are facing in Iraq. Were any of the five shot by the Iraqi forces they are training? Did a mortar round shot at their base injure a soldier? Has ISIS wounded a U.S. service member?

According to U.S. Central Command, which oversees military action in the region, the details of the wounded are not available, despite repeated requests for such basic information. The only specifics available are from a Washington Post story, which reported the first service member was wounded in March, just south of Baghdad, while in a guard tower. He was struck in the face by bullet fragments, according to the report, while coming under enemy fire.

Appearing before the Senate Armed Services Committee on Tuesday, Secretary of Defense Ash Carter repeatedly said the U.S. is in the region to “combat ISIS” but stopped short of saying the troops themselves are engaged in combat, even after senators repeatedly asked for clarity. Rather, Carter said Wheeler died in combat, in an isolated incident, while performing heroic acts.

Wheeler’s death forced the U.S. military to acknowledge, as Carter put it, that troops are “in harm’s way.” But the administration has said that while forces could, at times, face combat, they are not in a constant state of combat. The U.S. may be at war with ISIS in Iraq, but the troops fighting them are not “in an active combat mission in Iraq,” according to Pentagon spokesman Peter Cook. The U.S. military is there to train, advise, and assist, he said.

Cook would not say if the U.S. had conducted such raids in the past, which the Pentagon calls a combat mission. And yet Carter said the U.S. would take part in more such raids.

In announcing that the U.S. would fight ISIS, Obama was adamant the U.S. could “degrade and ultimately destroy” ISIS without U.S. combat troops. But the number of troops has slowly increased since that September 2014 pronouncement, from a few hundreds advisers to thousands of troops, at least some of them conducting combat missions.