Markets have been surging to new highs this year, propelled by a boom in artificial intelligence tech shares, which some analysts have cautioned is a bubble waiting to burst.A rally in tech stocks helped drive Seoul up more than two percent on Wednesday, with South Korean chipmaker SK hynix jumping 11 percent to hit a $1 trillion market capitalisation.The valuation makes SK hynix one of just three $1 trillion companies in Asia, along with Samsung Electronics and Taiwan's TSMC, according to Bloomberg -- all top manufacturers of chips used in AI systems. "In practical terms, the market heard one thing loud and clear. AI demand is no longer just about chips powering large language models. It is now about the memory systems required to feed those models at industrial scale," said SPI Asset Management analyst Stephen Innes.Investors were also monitoring negotiations between Washington and Tehran to end the Middle East war that have kept them guessing, with reports a deal was close undermined by fresh US strikes against Iran on Monday.Tehran accused Washington of breaching their ceasefire, in place since April 8, and warned that it was ready to retaliate against US targets across the Gulf.The US strikes pushed up the price of Brent North Sea crude, the international benchmark, by almost 4.5 percent on Tuesday to above $100 a barrel.But Brent and US benchmark West Texas Intermediate retreated more than two percent Wednesday on renewed hopes a deal to reopen the blockaded Strait of Hormuz was on track.The Middle East war, which began in late February, has disrupted the Hormuz strait, a vital oil and gas trading corridor, driving up energy prices and stoking global inflation."There remains an air of cautious optimism in markets that an MoU between the US and Iran will be signed and detailed throughout the week, although the central expectation and broad positive sentiment has been dented by the recent US defence strikes and Iran stating these measures breach the agreement," said Chris Weston, head of research at Pepperstone.Markets elsewhere in Asia were mixed. Taipei capitalised on the tech rally, climbing around 1.6 percent with Bangkok, Sydney and Wellington also up.Tokyo was flat however, while Hong Kong, Shanghai, Kuala Lumpur, Jakarta, Singapore and Manila dropped.Seoul was also boosted by Samsung Electronics posting strong gains, helped by its union approving a deal with management that secured huge annual bonuses and averted a major strike.In Europe, London opened down 0.5 percent while Paris and Frankfurt were both up.It comes after the S&P 500 and Nasdaq reached fresh records on Tuesday, with chip company Micron piling on nearly 20 percent to also hit a $1 trillion market cap.Key figures at around 0830 GMTBrent North Sea Crude: DOWN 2.6 percent at $96.98 a barrelWest Texas Intermediate: DOWN 3.1 percent at $91.00 a barrelHong Kong - Hang Seng Index: DOWN 1.1 percent at 25,328.23 (close) Tokyo - Nikkei 225: FLAT at 64,999.41 points (close)Shanghai - Composite: DOWN 1.3 percent at 4,093.73 (close)London - FTSE 100: DOWN 0.2 percent at 10,469.17Euro/dollar: UP at 1.1645 from 1.1635 on TuesdayPound/dollar: DOWN at 1.3445 from $1.3449 Dollar/yen: UP at 159.43 from 159.30 yenEuro/pound: UP at 86.61 from 86.49 penceNew York - DOW: DOWN 0.2 percent at 50,461.68 (close)