The S&P 500's around 27 percent surge this year may have left investors jumpy about whether a correction is on the cards, but a hoard of pent-up cash means the rally can continue, Deutsche Bank said.
The bank estimates around $169 billion in pent-up cash and short interest is likely to make its way into equities over the next three to four months.
(Read more: What bubble? We are still buying US stocks: UBS)
"Each year for the last four years from December to April, investors have moved cash out of money markets into bond and equity funds," it said. "We see equities as the beneficiary of cash re-deployment in 2014 as equity inflows have been running at a steady $23 billion monthly pace since February."
It expects the S&P 500 will see a 10 percent gain early in the new year, assuming around $120 billion of pent-up demand goes into U.S. equities, in addition to normal inflows from savings and buybacks.
(Read more: Why we're not keen on US stocks: Credit Suisse)