CNBC Daily Open: Fragile rebound in oil exports threatened by Iran attacks in Hormuz

Hello, this is Justina Lee writing to you from Singapore. Welcome to another edition of CNBC's Daily Open.

In stepping up attacks on tankers transiting through the Strait of Hormuz, Iran is threatening the recent precarious rebound in oil exports.

Stateside, U.S. President Donald Trump has allowed cheaper red-dyed diesel to be used more broadly in an attempt to bring down record-high fuel costs ahead of the U.S. midterm elections.

Over in tech, Anthropic is expanding its Claude Startups program, which allows members access to thousands of dollars' worth of the company's Claude products and credits.

Iran's move to step up attacks on tankers which are transiting through the Strait of Hormuz has led to renewed concerns over oil supplies among traders, as it threatens to disrupt the fragile rebound in oil exports through the crucial waterway.

According to the Joint Maritime Information Center, nearly 20 commercial ships have been attacked over the past month while sailing through Hormuz, the Persian Gulf or off the coast of Oman.

In addition, in the absence of a negotiated settlement or capitulation by Iran, worries still abound on whether the recent rebound is sustainable.

Meanwhile, to mitigate the impact of a historic fuel cost spike ahead of the U.S. midterm elections, President Donald Trump has temporarily allowed the use of cheaper red-dyed diesel, usually reserved for farm operations, to be used more broadly in America.

As this type of diesel is exempt from highway fuel taxes, truckers could save more than $100 per fill-up, according to the White House.

Besides Trump's plan to help Americans navigate high fuel costs, traders are also keeping watch on the U.S. trade deficit, which has hit $105.6 billion. This is the steepest deficit since the all-time gap in March 2025, recorded just before President Donald Trump's "liberation day" announcement of "reciprocal" tariffs against U.S. trading partners.

Over in markets, declines in Treasury yields and gains in key technology names helped to push the S&P 500 to a fresh all-time intraday high on Tuesday. The broad market index climbed 0.58% for a record close of 7,818.93, while the Dow Jones Industrial Average gained 0.49%. The Nasdaq Composite also hit a new all-time high during the session as well.

In Asia, markets closed mostly higher Tuesday. Japan's Nikkei 225 rose 1.05%, South Korea's Kospi fell 0.89% and Australia's S&P/ASX 200 advanced 0.57%. Mainland China markets were closed for a holiday on Tuesday.

Moving over to the tech sector, Anthropic said Tuesday that it is expanding its Claude Startups program. The program, which allows members to access thousands of dollars' worth of Anthropic's Claude products and credits, is part of the AI company's efforts to strengthen ties to fast growing companies and founders.

"Startups are often the first to push Claude to its limits," Beth Robertson, head of startups at Anthropic, told CNBC in a statement.

Startups that were founded within the past five years or funded within the past two years are able to apply, according to Anthropic.

—Justina Lee