Top Trump officials on Sunday turned up the heat on Russia following the deadly chemical attack last week in Syria.

Members of Trump's administration questioned Russia's commitment to past chemical weapons agreements and stressed that the U.S. will not let Russia cover for the regime of Syrian President Bashar Assad.

The U.S. launched a missile strike on a Syrian air base last week in retaliation for a chemical attack that killed civilians in northern Syria, which the U.S. has blamed on Assad’s forces.

On Sunday, members of Trump’s administration trained their fire on Moscow, which has been an ally to Assad in the country’s brutal civil war.

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U.S. Ambassador to the United Nations Nikki Haley said in an interview that the U.S. missile strike was intended to send a message to Russia.

"The entire administration was in agreement that this was something that had to be done. This was something that needed to tell Assad, 'Enough is enough,'" Haley told NBC's "Meet The Press."

"And this is something to let Russia know, 'You know what? We're not going to have you cover for this regime anymore. And we're not going to allow things like this to happen to innocent people.'"

Haley said the U.S. took a "moderate approach" but is capable of doing much more. She criticized Russia, saying its response to the chemical attack was to defend the Syrian government.

"Why were they that defensive that quick?" she questioned. "The idea of the casualties came after."

The U.S. is not going to allow Russia to "have Assad's back anymore," she said.

"What we are going to say is, 'Look, when you have a violation of the chemical weapons issue, and you've got a violation of Security Council resolutions over and over again, and you vetoed, seven times, to protect this war criminal, we're going to call you out on it,'" she said.

"We're going to call you out for the fact that you're covering up."

Secretary of State Rex Tillerson similarly criticized Russia, saying the country has not fulfilled its commitments.

In 2013, Russia and the United States brokered a deal to destroy Syria’s chemical weapons stockpile. Tillerson has slammed Moscow for either failing or neglecting to enforce that agreement.

Tillerson said Sunday he hopes Russia will "be supportive of a process that will lead to a stable Syria."

"I'm disappointed because I think the real failure here has been Russia's failure to live up to its commitments under the chemical weapons agreements that were entered into in 2013," Tillerson said during an interview on ABC's "This Week."

"Both by the Syrian government and by Russia as the guarantor to play the role in Syria of securing chemical weapons, destroying the chemical weapons and continuing to monitor that situation."

He attributed the chemical attack in Syria "in large measure" to a "failure on Russia's part to achieve its commitment to the international community."

"I hope Russia is thinking carefully about its continued alliance with Bashar al-Assad," he said, "because every time one of these horrific attacks occurs, it draws Russia closer into some level of responsibility."

The sentiment was echoed by national security adviser H.R. McMaster, who called for Russia to rethink its support for the Syrian president and made clear he believes Russia could be part of the "solution."

"Russia should ask themselves, 'What are we doing here?'" he said on "Fox News Sunday."

"'Why are we supporting this murderous regime that is committing mass murder of its own population and using the most heinous weapons available?'"

He said the renewed focus on Syria is a good opportunity for Russian leadership to re-evaluate its actions.

"Russia could be part of the solution," he said, adding that now, much of the world thinks Russia is "part of the problem."

McMaster also questioned what the Russians want the relationship with the U.S. to look like.

"Do they want it to be a relationship of competition and potential conflict? I don't see how that's in Russian interests. Or do they want it to be a relationship in which we can find areas of cooperation that are in mutual interests?" McMaster asked.

"How is it in anyone's interest that this conflict in Syria and this catastrophe in the greater Middle East continues?"

President Trump last week ordered the missile strike on the Shayrat air base in Syria after a chemical weapons attack in Idlib allegedly carried out by Assad's regime. The chemical strike left scores of civilians dead — including children — and left many others wounded.

The Pentagon said 59 Tomahawk missiles were launched, targeting aircraft, aircraft shelters, petroleum storage, ammunition supply bunkers, radars and air defense systems at the base.

Trump explained his decision Saturday in a letter to Congress, in which he said the decision to carry out the strikes was in America's "vital national security and foreign policy interests." He also warned the U.S. was prepared to take further military action if necessary.

Senior U.S. military officials said Friday the Pentagon is looking into whether Russia participated or assisted in the chemical attack in Syria, as well as an attack on a local hospital.

A senior official told reporters during a briefing at the Pentagon that "we have no knowledge of Russian involvement in this attack, but we will investigate any information that might lead us in that direction."

The Pentagon also cited Syria's 2013 use of chemical weapons to show the Russians failed to rein in the Syrian regime.

“Russia stepped in at the time and said they would guarantee the removal and elimination of Syria’s chemical weapons capability," an official said. "At the time they reported that the Syrians had turned in all of their chemical weapons.”

The Russians "failed to control the activities of their Syrian client," the official said.

If there's any evidence or credible accusations on Russian participation, "we'll follow up on that to the best of our ability."