As Western nations weigh strikes on Syria, Russian Foreign Minister Sergei Lavrov says Moscow has "irrefutable" evidence that an alleged chemical weapons attack in Syria was staged with the help of a foreign secret service.

Meanwhile, Russia's Deputy Prime Minister is criticizing tweets from US President Donald Trump that threaten air strikes. On Wednesday, Trump said missiles "will be coming" after the attack killed at least 40 people. But a day later, Trump seemed to take a step back, writing: "Never said when an attack on Syria would take place. Could be very soon or not so soon at all." Russia's foreign ministry says Moscow is ready to protect its people in Syria.