Trump administration rebuffs Russia's claims on chemical attack as 'false'

The Trump administration has broadened its assault on Russia's military involvement in Syria, offering new evidence that U.S. officials said showed that Moscow's explanation for a deadly April 4 chemical attack was false.

The new details from a declassified U.S. assessment add to tensions with Russia just as Secretary of State Rex Tillerson makes his first visit to Moscow and presses the Kremlin to drop its support for Syrian President Bashar al-Assad, the Washington Post reported.

The release of new intelligence findings projects a mounting determination by the Trump administration to counter Russia's explanation for the mass deaths in a rebel-held Syrian town and to justify last week's decision to launch missile strikes on the air base.

At least 70 people died of exposure to sarin, including numerous children.

The mounting public criticism of Russia takes place as Tillerson touches down in Moscow for talks with senior Russian officials, possibly including Putin.