Wall Street's main indexes ended Tuesday's session with gains as investors looked ahead to the Federal Reserve's monetary policy update while they digested a mixed batch of earnings reports.

The Fed kicked off a two-day monetary policy meeting. The central bank is widely expected to hold interest rates steady on Wednesday, and investors will monitor its statement and Fed Chair Jerome Powell's comments for clues about its plans.

Optimism that the Fed would pause rate hikes was offset by reactions to disappointing earnings reports and jitters over geopolitics.

Shares in heavy-machinery maker Caterpillar sank 6.7 percent as signs of slowing demand overshadowed a quarterly earnings beat. And drugmaker Amgen's stock fell 2.8 percent as third-quarter sales of some high-profile medicines were below expectations.

But with 10-year Treasury yields up just slightly for much of the day, some investors looked for bargains in light of recent weakness in stocks, said Sameer Samana, Senior Global Market Strategist at Wells Fargo Investment Institute.

"All roads right now lead back to long-term rates which impact equities," said Samana, adding that in stocks some investors may be encouraged by the idea that, "the recent sell-off brings us back to fairly valued from over-valued levels."

However the strategist was wary of upcoming events that could be huge catalysts for bonds and in turn equities. Along with the Fed's policy update, he is also waiting for the US Treasury Department's financing plans due out on Wednesday.

Analysts have said it is likely to boost the size of auctions for bills, notes, and bonds in the fourth quarter to fund a widening budget deficit. This would cause rates to rise further and hurt stocks, according to Wells Fargo's Samana.

On Friday, investors will also monitor the October US jobs report and the Treasury market's reaction.

The Dow Jones Industrial Average rose 0.38, to 33,053, the S&P 500 gained 0.65 percent, to 4,194 and the Nasdaq Composite added 0.48 percent, to 12,851.

Shares in flexible workspace provider WeWork fell 30 percent in extended trading after the Wall Street Journal reported that it planned a bankruptcy filing as soon as next week.

All three of Wall Street's major averages registered their third monthly loss in a row. (Reuters)