The S&P 500 and Nasdaq registered record closing highs for a second straight day on Tuesday, helped by a gain of more than 7 percent in Apple shares, while investors also awaited consumer prices data and a policy announcement from the Federal Reserve.

Apple shares jumped 7.3 percent to a record-high close and gave the S&P 500 and Nasdaq their biggest boosts after the stock declined in the previous session.

At its annual developer event that kicked off on Monday, Apple unveiled new artificial-intelligence features meant to increase the appeal of its devices, including an improved Siri virtual assistant that can answer a wider range of queries and accomplish more complicated tasks than earlier.

The S&P 500 technology index climbed 1.7 percent and also posted a record closing high.

The Consumer Price Index report will be released before the bell on Wednesday, and the US central bank's policy announcement is due later the same day.

The central bank is likely to leave interest rates unchanged but will release its updated economic projections and "dot plot," which shows where policymakers expect interest rates to stand this year and longer-term.

"Everybody is feeling uneasy, but the data and actions consumers are taking continue to point toward resiliency, and that tends to be overall fairly bullish," said Oliver Pursche, senior vice president and adviser for Wealthspire Advisors in Westport, Connecticut.

The Dow Jones Industrial Average fell 0.31 percent, to 38,747, the S&P 500 gained 0.27 percent, to 5,375 and the Nasdaq Composite added 0.88 percent, to 17,344.

General Motors gained 1.35 percent after the carmaker announced a US$6 billion share buyback plan. GM also cut its annual EV production forecast.

After the closing bell, Oracle shares rose 8 percent following the release of quarterly results. The stock ended the regular session down 0.5 percent. (Reuters)