SINGAPORE, Aug 4 (Reuters) - Asian markets were choppy on Tuesday as investors weighed whether strong U.S. corporate earnings would boost AI-related stocks in the region, while oil prices bounced back after attacks on shipping in the Strait of Hormuz.

MSCI's broadest index of Asia-Pacific shares outside Japan was down 0.1%, as volatile South Korean shares swung between gains and losses, last up 1.2%. Japan's Nikkei 225 nudged 0.2% upwards, while S&P 500 e-mini futures were 0.3% higher.

"The AI trade is maturing," Societe Generale analysts wrote in a research report. "Investor focus is increasingly shifting toward the sustainability of margins beyond 2026," they said, citing falling earnings expectations for South Korean technology stocks that have been at the centre of recent volatility.

Overnight, markets took confidence from data showing that U.S. manufacturing activity increased to the highest level in more than four years in July, sending the Dow Jones Industrial Average to a record close. 

With almost two-thirds of S&P 500 companies reporting for the second quarter, 84% have beaten earnings estimates, according to LSEG data.

Earnings announcements from Big Tech firms show "the AI capex boom remains intact," Eastspring Investments analysts, including Chief Investment Officer Vis Nayar, wrote in a note. 

Oil prices made limited gains in Asian trading, with Brent crude up 1.6% at $85.12 a barrel, after falling to a three-week low on Monday as U.S. President Donald Trump said he had held off on a fresh attack on Iran as a gesture of goodwill in peace talks. However, Tehran has denied that any negotiations are taking place.

Against the yen, the dollar was up 0.3% at 157.62 yen, rebuilding strength after coordinated intervention by U.S. and Japanese authorities to prop up the yen last week.

The yen remains about 4% stronger against the greenback compared with the levels a week ago that prompted official support and marked the first U.S. intervention in the Japanese foreign exchange market in 15 years.

But an auction of 10-year Japanese government bonds on Tuesday also drew weaker demand than the previous sale of sovereign debt, prompting a fresh bout of jitters. The yield on the notes jumped 3 basis points to 2.85%.

The yield on the U.S. 10-year Treasury bond was up 1.2 basis points at 4.694%.

The U.S. dollar index, which measures the greenback's strength against a basket of six currencies, was trading steady near the lowest levels of the past two months at 100.01.

Market pricing continues to indicate that September's Federal Reserve meeting will lead to a lift in interest rates.

Fed funds futures are pricing an implied 65% probability of a 25-basis-point hike at the U.S. central bank's next two-day meeting ending on September 16, according to the CME Group's FedWatch tool.

In cryptocurrencies, bitcoin was flat at $63,776.56 and ether slipped 0.3% to $1,862.40.