ZURICH, Jan 8 (Reuters) - The Swiss National Bank expects an annual profit of 21 billion Swiss francs ($23.72 billion) for 2020, the central bank said on Friday, as rising stock prices boost the value of its huge foreign currency investments to tame the Swiss franc.

The SNB made a profit of 13 billion francs from its foreign currency positions, and saw a valuation gain of 7 billion from the 1,040 tonnes of gold it holds.

The value of both increased during the coronavirus crisis as investors sought safe havens like gold and stock markets were boosted by low interest rates central banks use to support battered economies.

In the United States, for example, where the SNB holds stakes in nearly 2,500 companies including Apple and Tesla, the S&P 500 Index gained 16% and the Nasdaq Composite Index rose 44% during 2020.

The investments are a product of the SNB's foreign currency purchases, which it stepped up last year, leading to the country's being labelled a currency manipulator by the United States.

The SNB's profit was lower than the 48.9 billion francs it posted for 2019, as a weakening dollar reduced the level of profits when translated into francs.

The profit means the SNB can distribute 4 billion francs to the Swiss government and cantons, the same level as last year, although shareholder dividends will remain locked at 15 francs, the legal maximum.

Still, the profit is unlikely to be a cause for celebration for SNB Chairman Thomas Jordan.

"The SNB, like other investors, has benefited from the low interest rate environment brought in by central banks to help deal with the coronavirus crisis and which has boosted equity markets around the world," said UBS economist Alessandro Bee.

"But although this is good news for the SNB's financial performance, it's bad news for the bank's monetary policy as the low interest rates elsewhere keep appreciation pressure on the Swiss franc and limit the SNB's ability to adjust its own negative interest rates." ($1=0.8852 Swiss francs) (Reporting by John Revill; Editing by Clarence Fernandez and Michael Shields)