US says Syria warning also aimed at Russia, Iran

A warning by the White House that urged Syria's president to refrain from a potential chemical attack is also directed at his principal international backers, Russia and Iran, the U.S.'s UN ambassador said Tuesday.

The White House said late Monday should Bashar al-Assad's forces carry out another chemical attack "he and his military will pay a heavy price".

That warning, Nikki Haley said, extends to his allies in Moscow and Tehran.

Speaking before the House appropriations foreign operations subcommittee, Haley told lawmakers, "The goal is at this point not just to send Assad a message, but to send Russia and Iran a message.

"If this happens again, we are putting you on notice. And my hope is that the president's warning will certainly get Iran and Russia to take a second look, and I hope that it will caution Assad from the fact that we don't want to see innocent men, women and children hurt again," she said.

In a tersely-worded statement, the White House said it had detected "potential" signs of preparation for a chemical attack similar to those seen in the run-up to an April 4 attack the Trump administration blamed on Damascus.

The White House did not specify what evidence, if any, it has to back up its claim, and has yet to produce proof.

But the Pentagon identified the site of the alleged preparations as the Shayrat air base, the same location struck by dozens of U.S. cruise missiles after the Trump administration said it was used to launch the April 4 attack.

The missile strikes were the first time the U.S. purposefully targeted Assad's forces in the conflict's six-year history.