Stocks closed out Monday with slight gains after hovering around the flatline for most of the session, as investors seemed reluctant to jump in following a four-week rally and amid uncertainty over when the Federal Reserve would start paring back its stimulus.
Earlier, St. Louis Fed President James Bullard told CNBC the central bank's current $85-billion-a-month in bond purchases is a "torrid pace," adding "it's a very reasonable thing to do to substitute for the fact that you can't lower interest rates any further."
The Dow Jones Industrial Average squeezed out a gain of 23.57 points to end at 15,639.12, buoyed by ExxonMobil and Merck. The Dow Transportation index rose to hit a record high.
The S&P 500 climbed 6.29 points to finish at 1,767.93. The S&P logged its 15th time in the black in 19 sessions. The Dow and S&P are on pace for their biggest annual percentage gains since 2003.
The Nasdaq rose 14.55 points to close at 3,936.59.
The CBOE Volatility Index (VIX), widely considered the best gauge of fear in the market, ended near 13.
All key S&P sectors closed in positive territory, led by telecoms and energy.
(Read more: Why this sectorcould be a big risk to the rally)
"The bulls are making the case that we're up 25 percent for the year and in most cases, you run even further in the final two months—people are talking about 1,850 on the S&P," said Art Cashin, director of floor operations at UBS Financial Services. "We're up 25 percent for the year and we haven't been up that much since 1997. So not to dampen the parade, but we want to keep an eye on frothiness."
Last week, the Fed's monetary committee noted that it saw improvement in economic activity and labor market conditions but had "decided to await more evidence that progress will be sustained before adjusting the pace of its purchases."
(Read more: Yellen to meet with GOP before confirmation)
The central bank is not expected to begin tapering until 2014, due to recent economic data and the latest political impasse over government spending.
Investors will also be looking for further clues from the government's monthly employment report due at the end of the week. Economists expect to see 125,000 jobs added according to economists polled by Reuters, which would be the second-lowest number of jobs added of 2013, and that the unemployment rate has ticked up to 7.3 percent from 7.2 percent.
On the economic front, August factory orders slipped 0.1 percent following a 2.4 percent drop in July orders, while September factory orders climbed 1.7 percent, in line with estimates, according to the Commerce Department.
"I don't think the stock market is anywhere close to a bubble," Thomas Lee, chief U.S. equity strategist at JPMorgan told CNBC. "The median P/E in the market today is under 15 times and high yields tell us that the P/E should be over 17 times right now. So we're still trading at a huge discount and in terms of economic growth, I don't see any evidence that we're peaking."
Lee has a 1,775 year-end target on the S&P 500, but says the level will "not be any obstacle" for the market.
"There's a tilt that's going to happen back into cyclicals into year end," he said. "Some of the hedge funds are starting to increase their exposure to cyclical stocks, especially basic materials."
BlackBerry said it is abandoning a plan to sell itself and will instead raise some $1 billion and replace its chief executive, according to reports from the Globe and Mail newspaper. Shares plunged more than 15 percent.
Johnson & Johnson dipped after the drugmaker said it will pay $2.2 billion to the government to end multiple investigations into kickbacks to pharmacists and the marketing of pharmaceuticals for off-label uses.
Among earnings, Kellogg ticked higher after the food manufacturer reported a gain in quarterly profit, thanks to a decline in cereal-making costs, and said it would cut nearly 7 percent of its workforce by 2017.
Twitter raised its expected IPO price range to between $23 and $25 a share at 70 million shares, according to an SEC filing, up from a previously expected range of between $17 and $20 a share. Twitter's IPO is set to price on Wednesday, with shares trading on the New York Stock Exchange on Thursday.
—By CNBC's JeeYeon Park (Follow JeeYeon on Twitter:
On Tap This Week:
TUESDAY: ISM non-mfg index, Fed's Lacker speaks, Fed's Williams speaks; earnings from CVS, Michael Kors, Mosaic, Tesla, LiveNation, OpenTable
WEDNESDAY: Mortgage applications, Challenger job-cut report, leading indicators, oil inventories, Fed's Pianalto speaks, Samsung investors conf.; Earnings from Toyota, Chesapeake Energy, Ralph Lauren, Time Wanre, Qualcomm, Activision Blizzard, CBS, WholeFoods
THURSDAY: GDP, jobless claims, productivity & costs, Fed's Stein speaks, natural gas inventories, consumer credit, chain store sales; Earnings from Beazer, Wendy's, Disney, Priceline.com, Groupon, Nvidia, Annie's
FRIDAY: Nonfarm payrolls, personal income & statement, consumer sentiment, Fed's Williams speaks, McDonald's Oct. sales
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