Wall Street rose, as did US Treasuries, as the Federal Reserve began its two-day meeting.
The Federal Open Market Committee is not expected to announce an interest rate increase this time, though Wednesday's post-meeting press conference by Chair Janet Yellen will be closely watched for hints on when the central bank will do so.
Traders see a 22 percent chance of a Fed hike Wednesday, according to Bloomberg.
"They want to maintain market expectations for a rate hike in case they want to raise rates in December if conditions warrant one," Sam Bullard, a senior economist at Wells Fargo Securities in Charlotte, North Carolina, told Reuters.
Investors are also awaiting a policy decision from the Bank of Japan at the end of its meeting on Wednesday.
"Investors have become more comfortable knowing that a Fed rate hike decision will be put off until future meetings, but there is more uncertainty with what Japan will do," Paul Springmeyer, investment managing director at the Private Client Group, US Bank in Minneapolis, Minnesota, told Reuters.