(Adds announcement details, background on Ukraine conflict)
WASHINGTON, March 1 (Reuters) - The U.S. State Department has approved the possible sale of Javelin anti-tank missiles and launch units to Ukraine at an estimated cost of $47 million, the Pentagon said on Thursday.
The United States said in December it would provide Ukraine with defensive weapons.
Since Moscow's annexation of Crimea in 2014, Ukraine and Russia have been at loggerheads over a war in eastern Ukraine between pro-Russian separatists and Ukrainian government forces that has killed more than 10,000 people in three years.
Ukrainian President Petro Poroshenko said in December the weapons would be used to protect Ukrainian soldiers and civilians, but Russia said the U.S. decision would encourage those who support the conflict in Ukraine to use force.
The Pentagon said in a statement on Thursday the proposed sale would not alter the military balance in the region.
"The Javelin system will help Ukraine build its long-term defense capacity to defend its sovereignty and territorial integrity in order to meet its national defense requirements," it said.
Ukraine's government has asked to buy 210 Javelin missiles and 37 Javelin Command Launch Units, the statement said. The prime contractor will be a joint venture of Raytheon Co and Lockheed Martin Corp, it added.
Reporting by Mohammad Zargham; Editing by Eric Beech and Susan Thomas