The Pentagon has briefed President Trump on various military options the US can conduct in response to the poison gas attack in Syria that killed scores of civilians, and which Washington has blamed on the Syrian government, a U.S. official told Reuters.

Options include things like implementing a "no fly zone" or grounding aircraft used by Syrian President Bashar al-Assad's forces, an official quoted by Reuters said.

Another option also includes the use of Tomahawk cruise missiles to overwhelm Russian air defense systems used by the Syrian military. The official did not comment on how likely military action might be which, if any, options might be recommended by the Pentagon. According to the Intercept, this would be a “saturation strike” using dozens of cruise missiles designed to hit Syrian military targets —including military air fields — in an effort to limit future Syrian Air Force attacks on rebel positions, according to the two U.S. military officials.

Among the valid military targets in Syria would be Syrian military airfields, air defenses and other types of Syrian military installations. The official played down the idea that Russian military infrastructure might be a target.

What is most troubling, however, is that according to the quoted U.S. military officials, "the current proposal would likely result in Russian military deaths and mark a drastic escalation of U.S. force in Syria."

One U.S. military official said the decision to allow the strikes, which would kill Russians, signals a significant change in policy by the Trump administration. A decision by Trump to go forward with the plan would be a reversal from the Obama administration, which denied multiple air strike proposals that would likely cause Russian personnel casualties in Syria.

It remains unclear if Trump does launch a military campaign that ends up killing Russians, whether the narrative about Russia hacking the US elections to get Trump elected, will finally die.

Sarcasm aside, Reuters also said that Secretary of Defense James Mattis and National Security Adviser H.R. McMaster have been discussing the matter: Mattis is due to meet with Trump later in the day at the president’s Mar-a-Lago retreat, where a summit meeting with Chinese President Xi Jinping is underway. Speaking with reporters aboard Air Force One, Trump said that “something should happen” with Assad after the chemical attack, calling what happened in Syria “a disgrace to humanity.”

“There is no doubt in our minds, and the information we have supports, that the Syrian regime under the leadership of Bashar al-Assad are responsible for this attack,” Secretary of State Rex Tillerson told reporters in Florida on Thursday, adding that “there is no role for Assad” in Syria after this.

In case of an accelerated military escalation, the US Navy currently has two warships on alert in the East Medditerranean to strike in Syria if necessary, officials say cited by Fox News' Lucas Tomlinson, who adds that USS Ross and USS Porter are the 2 Navy warships in close proximity and ready to strike Syria, if necessary.

USS Ross and USS Porter are the 2 Navy warships in Med to strike Syria, if necessary. Both moved to Rota, Spain two years ago — Lucas Tomlinson (@LucasFoxNews) April 6, 2017

Trump's accusations against Assad put him directly at odds with Moscow, the Syrian president's principal backer. Trump's contemplated action also goes directly against Trump's tweets in 2013, when he urged against a military escalation in Syria.

The President must get Congressional approval before attacking Syria-big mistake if he does not! — Donald J. Trump (@realDonaldTrump) August 30, 2013

Earlier in the day, CNN reported that Trump has spoken to some members of Congress about military action in Syria. The president himself denied that report, however, according to Fox News correspondent Chad Pergram.

Reuters notes that any U.S. action against Syria's government would open a new front in Syria's fighting, with consequences that are difficult to foresee. Entering into such a confrontation might complicate the fight against Islamic State - a group seen to directly threaten the West - and very likely draw in Russia, which nearly entered into an armed conflict in 2013 when John Kerry backed off an airborne campaign targeting Assad in the last moment. The difference between now and 2013, however, is that Russia is already present in Syria, and is conducting regular military missions.

While Syrian chemical weapons storage facilities would also be valid military targets, it was not immediately clear how much intelligence the United States had collected on where Assad might be storing the kinds of nerve agent it believes was used in the most recent attack, assuming of course, that Assad did in fact conduct the poison gas attack.

The U.S. military, which has deployed around 1,000 troops in Syria, who are there without the invitation or consent of Syria's government, has long said its singular focus in Syria has been on the war against Islamic State, although many have said that the real motive from the beginning of US involvement in the conflict was the eliminate the Assad regime. In any case, the conflict is reaching a critical point as U.S.-backed forces isolate the city of Raqqa - the militants' de facto capital - ahead of an eventual assault.

Earlier on Thursday, Senator Rand Paul (R-Kentucky) announced he would oppose any military action without a vote in Congress.

“The President, if he decides to do something in Syria, he would come to Congress and ask for a declaration of war. Short of Congress voting on it, I'm opposed to illegal and unconstitutional wars," Paul told Fox News radio show ‘Kilmeade and Friends’.

Paul was promptly opposed by senators John McCain (R-Arizona) and Lindsey Graham (R-South Carolina), both of whom called for Trump to attack Syria.

"The United States should lead an international coalition to ground Assad's air force," they said in a joint statement Thursday. "This capability provides Assad a strategic advantage in his brutal slaughter of innocent civilians, both through the use of chemical weapons as well as barrel bombs, which kill far more men, women and children on a daily basis."

Earlier on Friday, Damascus denied using chemical weapons, saying that its jets targeted an arms depot where chemical weapons stockpiles were stored by Islamic State and Al-Nusra Front militants. Later in the day, the Russian Ministry of Defense confirmed that account of events.

The strike, which was launched midday Tuesday, targeted a major rebel ammunition depot east of the town of Khan Sheikhoun, Russian Defense Ministry spokesman Major-General Igor Konashenkov said in a statement. According to Konashenkov, the warehouse was used to both produce and store shells containing toxic gas. The shells were delivered to Iraq and repeatedly used there, said the spokesman, pointing out that both Iraq and international organizations have confirmed the use of such weapons by militants.

Finally, the biggest wildcard of all is what and how will Putin respond to an aggression by the US that directly threatens an ally - and national interest - of not only the Kremlin, but also China.