The Dow Jones Industrial Average increased 38.05 points, or 0.14 per cent, to 26,835.51. The S&P 500 fell 0.28 points, or 0.01 per cent, to 2,978.43, Xinhua news agency reported.
The Nasdaq Composite Index was down 15.64 points, or 0.19 per cent, to 8,087.44.
Shares of AT&T rose nearly 1.5 per cent, after US hedge fund Elliott Management took a stake of $3.2 billion in the US telecommunications giant.
Elliott Management said in a letter to AT&T that it plans to help the telecom firm "improve its business and realize a historic increase in value."
More than half of the 30 blue-chip stocks in the Dow extended gains around the closing bell, with shares of the widely-watched trade barometer Caterpillar up over 3.7 per cent, the best performers in the tally.
The healthcare sector posted the biggest losses of 0.92 per cent around market close, leading the six laggards of the 11 primary S&P 500 sectors.
Investors have digested the latest speech by the US Federal Reserve chair on Friday, which sent upbeat signals that the Fed would continue to take actions to prop up economic growth.
Fed Chairman Jerome Powell said on Friday that the US central bank will continue to act "as appropriate" to sustain the US economic expansion, which fueled hopes for further rate cuts.
"Our obligation is to use our tools to support the economy, and that's what we'll continue to do," Powell said at the University of Zurich. "We are clearly at a time where there is a range of views."
US stocks posted weekly gains last week, as investors' sentiment was boosted by the news that China and the US agreed to jointly create favourable conditions for trade talks in October.
( With inputs from IANS )