TOKYO, Japan: Japan's benchmark Nikkei index hit uncharted territory, briefly soaring past 44,000 for the first time as investors cheered clarity on U.S. auto tariffs and bets on bigger government stimulus at home.

The Nikkei 225 jumped as much as 1.24 percent to 44,185.73 in early trade before paring back gains. By the midday break, it settled 0.2 percent higher at 43,732.80 as some investors locked in profits. The broader Topix index also edged up 0.06 percent after climbing 0.77 percent earlier.

Optimism grew after Japan's chief tariff negotiator Ryosei Akazawa confirmed in a post on X that U.S. tariffs on Japanese autos would be lowered by September 16, easing uncertainty from a July trade deal.

Political shifts also buoyed sentiment. Prime Minister Shigeru Ishiba's resignation has opened the way for Liberal Democratic Party veteran Sanae Takaichi—who favors aggressive fiscal spending and looser monetary policy—to run for party leadership, Kyodo news reported.

Analysts at BofA Securities noted that, with the ruling coalition currently lacking a Lower House majority, the government may lean on expansionary policies to secure opposition cooperation. "We think the government is likely to adopt a more expansionary stance in the fiscal debates from the autumn," they said.

Chip-related stocks were among the day's biggest winners, echoing U.S. market gains led by Broadcom, which last week projected sharp revenue growth tied to artificial intelligence demand.

Advantest, a chip-testing equipment maker and Nvidia supplier, jumped more than 7 percent, making it the Nikkei's standout performer. Screen Holdings rose 3.74 percent, while Tokyo Electron gained nearly 2 percent.

The strong start for Tokyo markets followed another record-setting session in the U.S., where the Dow added 0.25 percent, the S&P 500 climbed 0.2 percent, and the Nasdaq advanced nearly 0.5 percent.