President Trump has met with Secretary General Jens Stoltenberg of NATO in Washington
The President refused to pull punches when he spoke of the "murderous" regime of President Bashar al-Assad.
He condemned what he called the "barbaric killing of children and babies" and thanked Nato members for standing by him in the joint press conference at the White House.
Speaking about relations with President Putin, who backs Assad, Mr Trump said there were problems.
He said: "Right now we are not getting along with Russia at all – we may be at an all time low.
"Russia is a strong country. The US is a very strong country.
"We are going to see how that all works out."
President Trump and Jens Stoltenberg met in the Oval Office while United States Secretary of State Rex Tillerson took part in a frosty meeting with President Putin.
NATO meets Donald Trump months after he described it ‘obsolete’
Wed, April 12, 2017
The White House says the President will use the meeting as an opportunity to reaffirm his commitment to NATO
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U.S. President Trump meets with NATO Secretary General Stoltenberg at the White House in Washington
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Donald Trump was strong on Russia as he claimed the US will not be intimidated
Trump said it was unlikely Russia did not know about the airstrike on Idlib which killed more than 28 children.
He said he would "like to think" Putin was unaware of the attack.
He said: "Everybody in this room saw too many times babies dying, father's holding children in their arms, dead children.
"That's a butcher. I felt we had to do something about it.
"I have absolutely no doubt we did the right thing."
Donald Trump holds a joint press conference with Nato Secretary General, Jens Stoltenberg
Russia was left furious last week when Trump ordered the bombing of an airbase in Idlib Province, Syria, to take out a strategic air base.
The Republican leader of the US ordered multiple strikes after images of children dying in the street after a chemical weapons attack emerged.
Russia and its ally, president Bashar al-Assad of Syria denied the Syrian regime had attacked civilians.
Putin accused the US of undermining Moscow's strategic missions in Syria.
The secretary general for Nato said the world must find new ways to engage with Russia.
However, he said anyone involved in the use of chemical weapons would be dealt with.
He said: "The only way to deter Russia is to be strong.
"Any use of chemical weapons is unacceptable and cannot go unanswered. Those responsible must be held accountable."
Today's meeting marked 68 years since the signing of the North Atlantic Treaty.
President Trump said: "Nato allies defeated communism and liberated captive nations of the cold war
"It secured the longest unbroken period of peace Europe has ever known.
"Our common security is always number one and our common devotion to human dignity and freedom."
Chief Stoltenberg met with Donald Trump in the White House
Mr Stoltenberg praised Mr Trump for his "dedication" to Nato, including supporting Montenegro joining this week.
The Secretary General said Europe and the US are united by their membership.
He said: "Peace in Europe is important for the security and prosperity of North America.
"A strong Europe is good for the United States."
Donald Trump grins as he meets Secretary General Jens Stoltenberg of NATO
Chief Stoltenberg said the pair shared an "excellent and productive" meeting with Trump.
He said: "Nato must do more in the global fight against terrorism.
"Training local forces is one of the best weapons we have.
"Nato has the experience, expertise and staying power to make a real difference."
Again, the pair said every member of Nato must pay its fair share – set at two per cent of the country's GDP.
Mr Trump said the Transatlantic alliance was adapting to the broader mission against Islamic militants.
He said: "I said it was obsolete. It's no longer obsolete."
President Putin has backed Assad but Nato has condemned the actions of the regime
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