US stock index futures dropped on Tuesday, as worries about the scale of consensus at the Federal Reserve in favor of deeper cuts in interest rates ate into the positive sentiment that drove indexes to record highs last week.

Initial price action pointed to losses of 0.2%-0.3% for the Dow and S&P, and a big half percent fall for the Nasdaq which included a dip in shares in Apple ahead of its quarterly results release later in the day.

Wall Street's main indexes have had a slow start to the week, retreating on Monday, and participants are bracing themselves for what message the Fed will send if it pushes ahead with a well-telegraphed move to ease policy that has driven stocks higher since May.

With a quarter point reduction in rates fully priced-in, investors will watch for how Fed Chairman Jerome Powell manages debate about whether the stimulus is necessary and what that says about the attitude of the US central bank to doing more in the months ahead.

"The rate cut, which nearly everyone expects tomorrow, is not so much based on current data as it is being cast as an insurance policy that is cheap to take, so the argument goes, because price pressures are low," said Marc C. Chandler, Chief Market Strategist at Bannockburn Global Forex.

With inflation data due later on Tuesday, he pointed to an uptick in core inflation since January which the Fed could emphasize as a way of quelling expectations for more action.

As earnings season enters its third week, Apple Inc's report after hours will provide a clear gauge on the impact of trade tensions with China on growth. Shares of the iPhone maker dipped 0.6%.

Although trade talks between the world's two biggest economies resumed on Tuesday, expectations among traders for any breakthrough are limited.

Corporate earnings so far have been robust with nearly half of all S&P 500 companies that have posted second-quarter earnings, 76.1% have beaten bottom line estimates, according to Refinitiv data.

Goldman Sachs said on Monday it was lowering its earnings estimates for the benchmark index, citing weakness in economic activity and the outlook for margins but said Wall Street is still set to extend its decade-long bull run into another year.

Also on tap is a Commerce Department report, due at 8:30 a.m., which is expected to show US consumer spending rose 0.3% in June after rising 0.4% in May.

The core personal consumption expenditures (PCE) data, the Fed's preferred measure of inflation, is expected to be unchanged for the month of June.

At 7:19 a.m. ET, Dow e-minis were down 58 points, or 0.21%. S&P 500 e-minis were down 10 points, or 0.33% and Nasdaq 100 e-minis were down 45.25 points, or 0.57%.

Among other stocks, shares in Merck & Co Inc rose 3.1% after the drugmaker reported quarterly profit above expectations.

Procter & Gamble Co gained 4.1% after the consumer goods maker beat estimates for quarterly revenue boosted by price hikes and strong demand for its beauty products.

Pfizer Inc was set to fall for another day, last down 2.3%, after Morgan Stanley downgraded the drugmaker's stock to "equal-weight."