WASHINGTON, Apr. 8 - The United States is considering sending warships into the Black Sea in the next few weeks in a show of support for Ukraine amid Russia's increased military presence on Ukraine's eastern border, a US defense official told CNN Thursday.

The US Navy routinely operates in the Black Sea, but a deployment of warships now would send a specific message to Moscow that the US is closely watching, the official said.

The US is required to give 14 days notice of its intention to enter the Black Sea under a 1936 treaty giving Turkey control of the straits to enter the sea. It is unclear if a notice has yet been sent.