Government bond yields are down sharply after the Treasury Department said it would at least double the size of its buyback operations for longer-term notes and bonds.

Treasury said buyback operations for 10-, 20- and 30-year bonds would be increased to at least $4 billion per operation from their current maximum of $2 billion. The change will come into effect on Sept. 9 and extend though Nov. 4.

Treasury's buyback operations are meant to improve liquidity in the bond market by reducing the amount of older securities. Treasury's website states that the agency "does not currently intend to use buyback operations to mitigate episodes of acute market stress."

Yields on longer-term Treasurys have climbed in recent weeks, with the yield on the 30-year bond reaching a 19-year high.

The 30-year bond yield was recently 5.207%, according to Tradeweb, down from 5.284% Tuesday.