Benchmark indices have erased early gains and have slipped into negative zone weighed down by IT and capital goods shares.
By 9:40, the Sensex was lower by 38 points at 21,156 mark and the Nifty slipped by 17 points at 6,297 levels.
Shares will remain firm for most of the thinly-traded week ahead, as inflows from foreign institutional investors (FIIs) are expected to continue despite the US Federal Reserve starting to withdraw its stimulus programme from January 1.
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Stock markets are expected to continue their bull run this week amid robust overseas investments while global cues and quarterly earnings, starting next month, will dictate near-term trend on the bourses, say experts.
On the global front, Japan's Nikkei stock average hit a fresh six-year high on Monday, its final trading day for 2013, and is set to close the year up more than 55% to mark its biggest annual gain since 1972. The Nikkei advanced 0.3% to 16,230.23 in mid-morning trade, on track for a ninth straight day of gains, which would be its longest winning streak since July 2009.
Japanese markets will be closed for the New Year holiday from December 31 to January 3, and will reopen on January 6.
US stock indexes closed mostly flat on Friday, with the Dow snapping a six-day streak of record closing highs after investors took a break from this week's rally.
Shares of Twitter Inc, the social media company that has nearly tripled in value since going public in early November, slid 13% to close at USD 63.75 after investors took profits. Twitter was the most actively traded stock on the New York Stock Exchange on Friday.
The tech-heavy Nasdaq fell 0.25%, with leaders like Apple off 0.7% at USD 560.09 and Facebook Inc. down about 4% at USD 55.44. The Nasdaq has surged 37.7 percent this year, making it the best performer among the three major US stock indexes.
Back home, BSE Capital Goods and IT indices have slipped by nearly 1% each.
The main losers on the Sensex at this hour include L&T, Wipro, ICICI Bank, Tata Power, Infosys, BHEL and Bajaj Auto.
Sesa Sterlite has rallied 4% to Rs 209 in early morning deals on the BSE after the company said it has received permission from the Honorable Supreme Court appointed Monitoring Committee to resume mining activities at its Karnataka mine.
The broader markets are outperforming the benchmark indices- BSE Midcap and Smallcap indices are up marginally.