Pre-market: Sensex may swing to F&O tune

Following smart gains in the US indices, the Sensex is likely to open on a positive note. However, the latter half of the day the action will shift to derivatives expiry for November series.

The index is likely to face resistance around 13,665-13,680-13,695 levels, while on the downside the index may find support around 13,570-13,555-13,540 levels.