WASHINGTON (AP) — The United States and Russia are trading conflicting assertions about who launched a chemical weapons attack in Syria that killed 72 people.

The White House says Syrian President Bashar Assad's government is responsible. But Russia says anti-Assad rebels are to blame. Russia's military says the chemicals were dispersed when Syrian warplanes bombed a facility where rebels were building chemical weapons.

Officials say Secretary of State Rex Tillerson will discuss Syria with Russian leaders next week when he visits Moscow. It's the first announced visit by a top U.S. official to Russia since President Donald Trump's inauguration.

The U.N. Security Council plans an emergency session midday Wednesday on the attack. And Trump is expected to face questions about it during an afternoon news conference with Jordan's King Abdullah II.