WASHINGTON -- Intense discussions are ongoing over how, and when, to punish Syria following an apparent chemical attack this week. The heated debate is taking place between President Trump, top military advisers and European countries that would join any military response.

A strike could be carried out by long-range missiles launched from submarines, ships or aircraft and targeted at Syrian military installations.

But Russian President Vladimir Putin's top general has vowed to shoot down any missiles that threaten Russian personnel in Syria.

The strike would come less than a week after a suspected chemical weapons attack that the White House blames on both Syria and Russia.

"We're again confident that both Syria had responsibility in this chemical weapons attack, but we also hold Russia responsible for their failure to stop chemical weapons attacks from taking place," said White House press secretary Sarah Sanders.

Both Great Britain and France appear ready to join the strike. Nikki Haley, the U.S. ambassador to the United Nations, said all three countries have concluded chemical weapons were used.

"Did a chemical weapons attack happen? Yes, the U.S. has analyzed: yes, it has happened," Haley said. "The U.K. has analyzed: yes, it has happened. France has analyzed: yes, it has happened. Three separate analyses all coming back with the same thing: there is proof that this happened."

Videos and blood samples indicate victims suffered symptoms consistent with both chlorine gas and a nerve agent. Ambassador Haley told the U.N. Security Council that Syria's president, Bashar Assad has a history of using chemical weapons.

"The United States estimates that Assad has used chemical weapons in the Syrian war at least 50 times," Haley said. "We know who did this. Our allies know who did this. Russia can complain all it wants about fake news, but no one is buying its lies and its cover ups."

This would be the second time the U.S. has struck Syria in retaliation for the use of chemical weapons. The aim would be to do greater damage than the last time but without hitting any Russians, who will probably be given a heads up that the missiles are coming.