"It's very hard to understand how a political solution could result from the continuation of the Assad regime", McMaster said on "Fox News Sunday". He reiterated previous Russian assertions that the chemical weapons attack last week that prompted a US Tomahawk missile barrage on a Syrian air base was either a rebel provocation or caused by Syrian warplanes hitting a rebel chemical weapons facility.
UN Ambassador Nikki Haley said that new actions could be taken against Syria.
PALM BEACH, Fla. - The White House is circulating a letter President Donald Trump sent to the leaders of both houses of Congress explaining his decision to order military strikes on a Syrian air field.
White House national security adviser H.R. McMaster says that while the USA would push for regime change in Syria, "We're not the ones who are going to effect that change". "Once the ISIS threat has been reduced or eliminated, I think we can turn our attention directly to stabilizing the situation in Syria", he said, using an alternative acronym for ISIL.
"Congress needs to work with the president to try and deal with this long-term strategy, lack of strategy, really, in Syria", he said.
The statement by the group, published on media outlet Ilam al Harbi (War Media) said: "What America waged in an aggression on Syria is a crossing of red lines".
The reported investigation follows Moscow's condemnation of the U.S. missile strike on the Syrian airfield.
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Tillerson would "deliver that clear and coordinated message to the Russians", he said.
"Our priority is first the defeat of ISIS", Tillerson told George Stephanopoulos on ABC. "And Russia was never part of the targeting".
The US and United Kingdom have blamed Russia for being complicit in the horrific deaths of innocent Syrians in last week's chemical attack and the federation is facing the threat of fresh worldwide sanctions over its support for the dictator.
"Let's be quite clear, the Assad regime is a client state of Russian Federation".
Trump ordered the missile strikes on the Syrian air base after blaming Assad for the chemical weapons attack, which killed at least 70 people, many of them children, in the Syrian town of Khan Sheikhoun.
The official said the drone's presence could not have been a coincidence and that Russian Federation must have known the chemical-weapons attack was coming and that victims were seeking treatment. She said late last month that "our priority is no longer to sit there and focus on getting Assad out".
Russian President Vladimir Putin on Tuesday warned of future chemical weapons "provocations" in Syria to frame President Bashar Assad, just as Washington's top diplomat arrived for talks in Moscow. According to Syrian state media, the U.S. bombing left nine people, including four children dead.