U.S. President Barack Obama vows to pursue a diplomatic initiative from Russia over Syria's chemical weapons - while voicing skepticism at the plan.

SOUNDBITE: U.S. PRESIDENT BARACK OBAMA, SAYING:

"It's too early to tell whether this offer will succeed. And any agreement must verify that the Assad regime keeps its commitments. But this initiative has the potential to remove the threat of chemical weapons without the use of force, particularly because Russia is one of Assad's strongest allies."

In an address to the nation from the White House, Obama said Russia's proposal for Syrian President Bashar al-Assad to give up chemical weapons - could head off his plan for a limited military strike in Syria.

Obama said U.S. and Russian officials would discuss the initiative - and he would talk with Russian President Vladimir Putin.

Meanwhile, Obama said he has asked the U.S. Senate to put off a vote requesting the authorization for military force in Syria.

SOUNDBITE: U.S. PRESIDENT BARACK OBAMA, SAYING:

"I have, therefore, asked the leaders of Congress to postpone a vote to authorize the use of force while we pursue this diplomatic path."

Obama used much of the speech to lay out his case against Syria - saying evidence showed the Syrian government was behind an August 21 chemical weapons attack that killed more than 1400 people - including more than 400 children.

SOUNDBITE: U.S. PRESIDENT BARACK OBAMA, SAYING:

"If we fail to act, the Assad regime will see no reason to stop using chemical weapons. As the ban against these weapons erodes, other tyrants will have no reason to think twice about acquiring poison gas, and using them."

Obama argued the Assad government should face consequences - because if the world does not act - it will embolden the U.S.'s adversaries.