Story by the Associated Press; curated by Dave Urbanski

WASHINGTON (AP) — A senior administration official said Secretary of State John Kerry will travel to the Ukrainian capital of Kiev Tuesday to meet with government officials.

US Secretary of State John Kerry speaks on Syria at the State Department in Washington, DC, on August 26, 2013. The United States said Tuesday that chemical weapons had been used against Syrian civilians and warned President Barack Obama would demand accountability for this 'moral obscenity.' Employing his strongest language yet, Kerry said Washington was still examining evidence, but left no doubt that Bashar al-Assad's regime would be blamed. Credit: AFP/Getty Images

U.S. Secretary of State John Kerry (Image source: Getty Images/AFP)

Kerry’s trip comes as the U.S. and other Western nations weigh a response to Russia’s military advance into Ukraine. Kerry has raised the possibility of issuing economic sanctions and visa bans, freezing Russian assets and levying trade and investment penalties.

The official said the U.S. now believes that Russia has complete operational control of the Crimea peninsula, a pro-Russian area of Ukraine. The official added that the U.S. believes there are more than 6,000 Russian air and naval forces in the region.

The official was not authorized to publicly discuss the situation and insisted on anonymity.

This is breaking news; updates will be added.

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