Morning Bid: The biggest day for markets this year

By Jamie McGeever

(Reuters) - A look at the day ahead in Asian markets.

Asian assets have rarely been exposed to as many market-moving triggers in one day than they will be on Wednesday, with the Bank of Japan rate decision and China's purchasing managers index reports topping a packed policy, data and corporate calendar.

Investors are also bracing for second quarter GDP estimates from Taiwan and Hong Kong, inflation numbers from Australia, and earnings from corporate heavyweights including HSBC, Samsung, Panasonic, Mitzuho and Sumitomo.

All that follows heavy after-the-bell selling of U.S. Big Tech on Tuesday after Microsoft warned of slow returns on AI technology spending, and comes ahead of the Federal Reserve's rate decision on Wednesday.

With so much event risk looming - it's month-end too - an escalation in Middle East tensions could not have come at a more sensitive time for markets. World stocks, the S&P 500, Nasdaq and U.S. Treasury yields all slid on Tuesday.

The dollar on Tuesday hit a three-week high on an index basis, nudged above 155.00 yen, and was fixed at its strongest level since November against the Chinese yuan. But it ended U.S. trading on the defensive.

The BOJ's policy decision is on a knife-edge, at least according to money market pricing, which indicates a 55% likelihood the BOJ will raise rates by 10 basis points. That's down from a 60% probability earlier this week.

If the central bank stands pat and delivers a dovish message, the dollar could head back up to intervention territory around 160.00 yen. A hike and hawkish stance could bring 150.00 into view.

While policymakers are expected to outline plans to taper the bank's huge bond-buying stimulus, a rate cut is a close call. They may wait and see what the Fed does later on Wednesday, making a move in September more likely.

While the Bank of Japan deliberates how it will tighten policy, the People's Bank of China is going the other way, and PMIs from Beijing on Wednesday will give the first glimpse of how the world's second largest economy performed in July.

Expectations are being kept low - the manufacturing PMI is forecast at 49.3, according to a Reuters poll, down from June's 49.5 and marking the third month of contraction in a row.

More stimulus is needed if 2024 GDP growth is to reach Beijing's 5% target, especially with U.S. tariffs coming down the pike. Chinese leaders on Tuesday signalled that stimulus will be directed at consumers, deviating from their usual playbook of pouring funds into infrastructure projects.

Elsewhere, Australian inflation in June is expected to come in at 3.8%, up from 3.6% in May, while annual GDP growth in Taiwan is seen slowing to 4.8% in the April-June period from 6.6% in Q1.

Here are key developments that could provide more direction to markets on Wednesday:

- Bank of Japan policy decision

- China 'official' PMIs (July)

- Taiwan GDP (Q2)

(Reporting by Jamie McGeever)