From Rocky Swift

TOKYO, May 21 (Reuters) - Japan's Nikkei index rose more than 3.5 percent on Thursday, posting its biggest gains in two weeks, boosted by renewed enthusiasm for technology stocks and easing geopolitical tensions related to a potential war with Iran.

The benchmark Nikkei 225 index climbed 3.58 percent to 61,945.34 points, and is on track for its biggest daily gain since May 7 if current momentum continues. The broader Topix index rose 2.21 percent to 3,875.34 points.

The Nikkei index followed Wall Street's gains ahead of the release of results from AI leader Nvidia, which forecast sales higher than market estimates.

Oil prices fell sharply overnight after US President Donald Trump said negotiations to end the war with Iran were in their final stages, easing supply concerns.

Investor confidence was boosted by the averting of a Samsung Electronics strike that could have disrupted South Korea's economy and global chip supplies, and by reports that OpenAI is preparing for its initial public offering. Shares of SoftBank Group, a major investor in the company and other AI ventures, jumped to their daily limit.

"The market is being led by AI and semiconductor stocks following recent developments, including Samsung Electronics averting a strike and Nvidia's results," said Wataru Akiyama, equity analyst at Nomura Securities.

He added, "We are seeing gains in a wide range of sectors due to lower crude oil prices."

156 stocks listed on the Nikkei index rose, while 69 declined. SoftBank Group led the percentage gainers, climbing 19.9 percent, followed by Socialex, which jumped 17.2 percent, and Ibiden, which increased 15.2 percent.