(Reuters) -U.S. stock index futures edged lower on Tuesday as conflict in the Middle East entered its fifth day, dampening global investor confidence ahead of the Federal Reserve's upcoming policy meeting.

Iran and Israel's air war, which began on Friday when Israel attacked Iran's nuclear facilities, has raised concerns that the conflict could create bottlenecks for oil exports from the oil-rich Middle East.

U.S. energy stocks rose in premarket trading as oil prices remained elevated on the uncertainty. Shares of Chevron and Exxon were up nearly 1% each.

The surge in oil prices comes ahead of the Fed's monetary policy decision on Wednesday, when policymakers are widely expected to keep interest rates unchanged.

Money market moves show traders are pricing in about 48 basis points of rate cuts by the end of 2025, with a 59% chance of a 25-bps rate cut in September, according to CME Group's Fedwatch tool.

At 5:33 a.m. ET, Dow E-minis were down 269 points, or 0.63%, S&P 500 E-minis were down 37.25 points, or 0.62%. Nasdaq 100 E-minis were down 138.5 points, or 0.63%

U.S. Senate Republicans late on Monday unveiled proposed changes to President Donald Trump's sweeping tax-cut bill that had cleared the House of Representatives in May.

"The Senate's version of tax legislation looks broadly similar to the House-passed version in its near-term fiscal effects but would likely cost ... a few hundred billion dollars more over the next decade," said Goldman Sachs strategists in a note.

Solar stocks dipped after the Senate's changes to Trump's tax-cut bill revealed a phase-out of solar, wind and energy tax credits by 2028.

Shares of Enphase Energy, which makes solar inverters, dropped 17%. Solar panel sellers Sunrun fell 27.5% and SolarEdge Technologies dropped more than 21.6%. First Solar lost nearly 11%.

Shares of nuclear power companies rose after the Senate extended credits for nuclear energy to 2036. Oklo was up 1.9% and Nano Nuclear Energy rose 2.2%.

As investors flock to traditional safe-haven assets amid heightened geopolitical uncertainty, a rise in U.S. Treasuries pushed yields lower across the curve. Yields on the benchmark 10-year fell about 3 basis points to 4.42%.

Among other movers, Eli Lilly is in advanced talks to acquire gene editing startup Verve Therapeutics for up to $1.3 billion, according to a report. Shares of the drugmaker fell 1.2%, while Verve advanced 82.9%.

Key data for the day includes monthly retail sales and import prices scheduled at 08:30 a.m. ET.