The upcoming US earnings season may not be the time for investors to buy aggressively, because this year's winners already reflect earnings optimism.

The first-quarter reporting period, which begins today with results from aluminium company Alcoa, follows three months of solid gains that have brought stocks close to two-and-half-year highs.

Other top names reporting next week are JP Morgan Chase & Co, Bank of America and Google.

Some gains have been in anticipation of a strong earnings season, particularly for the energy and other cyclical sectors, analysts said, raising questions about whether this quarter’s reports will be enough to keep the recent uptrend intact.

Stocks have been going up “in anticipation of earnings that are going to be what the real consensus is basically expecting,” said Ken Fisher, chairman and chief executive of Fisher Investments.

Some investors see the rise in energy and other stocks that benefit when the economy starts to recover as unsustainable and have been paring back positions.

“We believe commodity inflation is probably near a peak as is the interest level in many deeper cyclicals” including the energy sector, said Tom Galvin, managing director and lead portfolio manager at Columbia Management.

Overall, first-quarter earnings for S&P 500 companies are expected to have increased 11.4 per cent from a year earlier, but that’s down slightly from a forecast of 13 per cent on 1 April, according to Reuters data.