(The opinions expressed here are those of the author, a

columnist for Reuters.)

By Mike Dolan

June 24 (Reuters) -

What matters in U.S. and global markets today

By Mike Dolan, Editor-at-Large, Finance and Markets

An 8% plunge in the high-flying U.S. chip stock index on Tuesday

marked a jarring injection of volatility into mid-year trading.

Memory chipmaker Micron Technology fell around 13%, reversing

all its gains from the day before, ahead of its earnings update

today.

For an index that had doubled so far this year, maybe it just

ran out of steam, but the 10% retreat in South Korea's

chip-heavy and volatile KOSPI earlier in the day won't have

helped either.

SoftBank CEO Masayoshi Son thinks it's "blasphemy" to think of

AI as a bubble, though after this week's latest wobble, others

may not be as confident.

I'll get into that and more below.

But first, check out my latest column on why a Greenspan-style

approach to asset bubbles could be cause for concern under Kevin

Warsh's Federal Reserve.

And listen to the latest episode of the Morning Bid daily

podcast. Subscribe to hear Reuters journalists discuss the

biggest news in markets and finance seven days a week.

BUBBLE OR BLASPHEMY?

The KOSPI, other Asia bourses and U.S. futures stabilised a bit

overnight after Tuesday's tech selloff, which saw the Nasdaq

shed more than 2%. But the episode will prompt another bout of

questions around stretched tech valuations.

Micron's earnings will be the sector's next test as

investors look to learn more about the AI-driven memory chip

demand that's propelled the company's stock up more than 200%

this year.

SpaceX's damp squib over the past week since its IPO was another

sideshow, with the rocket maker falling precipitously from its

post-IPO peak. But its shares found a level above the listing

price on Tuesday.

One factor gnawing at tech is pumped-up Fed rate-rise

expectations since last week's policy meeting - and the wild

divergence in forecasts on what might happen from here. Bank of

America expects three hikes through next January, for example,

while Citi still expects three cuts.

U.S. business surveys for June were above forecast, meantime,

while oil prices continued to ebb toward four-month lows on

U.S.-Iran talks and increased shipping activity in the Gulf,

with Brent crude dipping below $76 per barrel.

In currency markets, the dollar extended recent gains on

rate-hike bets, with the dollar index reaching a 13-month high

and attention staying fixed on possible Bank of Japan

intervention to prevent the greenback from hitting 40-year highs

against the yen.

An intriguing story about how Japan's government is looking for

better ways to manage its $1.3 trillion foreign exchange

reserves is also grabbing attention.

In single stock moves, FedEx stock fell 6% out of hours on

worries about tighter margins in its latest earnings update on

Tuesday. And private credit jitters continue to rumble as Morgan

Stanley joined Apollo this week with the latest report of heavy

redemptions from its flagship funds.

Chart of the day

Donald Trump's overall approval rating dropped to 34%, according

to the latest Reuters/Ipsos opinion poll, a return to the lowest

level of the Republican president's second term that was last

touched in an April survey.

Trump's approval rating on the cost of living, at 22%, was

near the lowest level of his presidency and below the rating of

his Democratic predecessor Joe Biden at the end of his

presidency. Only 24% of Americans think the war with Iran was

worth the costs, the poll showed.

Today's events to watch

* U.S. corporate earnings: Micron Technology

* U.S. Q1 current account (8:30 a.m. EDT), May new home

sales (10 a.m. EDT)

* U.S. 2-year floating rate note auction (11:30 a.m. EDT),

5-year note auction (1 p.m. EDT)

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Opinions expressed are those of the author. They do not reflect

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committed to integrity, independence, and freedom from bias.