US Treasury yields ended lower on Tuesday because market participants preferred to purchase the safe-haven asset ahead of the conclusion of the US Federal Open Market Committee policy meeting later today.Yield on the 10-year US Treasury note ended 4 basis points lower to settle at 0.84%. Market participants are waiting for the Fed's outlook on economy.The US central bank will give economic projections for the first time since December. The projections would be crucial to gauge the possibility of any stimulus and the trajectory of US interest rates.Market participants are also waiting for a word from the Fed on yield curve control, a policy measure which has been in discussion given the steepness of the US Treasury yield curve since March. In yield curve control, the Fed would be able to buy as many bonds as necessary to keep yields from rising above a target.The uncertainty ahead of the FOMC meeting outcome has prompted investors to book profits in equities globally. Since March, equities have risen sharply as central banks across the world have announced monetary stimulus and governments have come out with fiscal measures to support the economy. In the last few weeks, hope of a faster economic recovery has also supported equities.