* Oil surges towards $100 on Middle East tensions

* US tech firms' spending plans lift Asian chipmakers

* ECB expected to hold rates, talk hawkish

* Yen languishing at 40-year lows

(Updates ahead of ECB interest rate decision)

By Marc Jones

LONDON, July 23 (Reuters) - A spike in oil prices toward

$100 a barrel drove Europe's government borrowing costs to

long-term highs on Thursday as reignited inflation worries

prompted some hawkish signals from the European Central Bank as

it held rates steady.

Share markets were also on the back foot as an earnings miss

from chipmaker STMicroelectronics sent its shares

tumbling 15% and after Google-parent Alphabet plans announced it

would ramp up AI spending by another $15 billion to $200 billion

for the year.

The main focus remained on the renewed surge in oil prices

- and global borrowing costs - following the

re-escalation of the Iran war.

The Iran-aligned Houthis said on Thursday they had struck

two Saudi oil tankers as part of a naval blockade on Saudi

Arabia, threatening to create a second chokepoint on global oil

supplies alongside Iran's near-closure of the Strait of Hormuz.

The U.S. military carried out a new round of strikes on

Iran, marking a 12th successive night of American attacks and

prompting further Iranian retaliation.

Brent prices jumped almost 5% to more than $98 a barrel,

putting the psychological $100 threshold well within reach

again.

Germany's 10-year bund yield, the benchmark for euro zone

borrowing costs, also rose above 3.2% for the first time since

2011 -a time when oil was also on a tear and the bloc's debt

crisis was about to break out again too.

"Uncertainty remains high and the full inflationary impact

of the energy shock has yet to play out," the ECB said as it

held rates at 2.25%, having lifted them in June.

"The Governing Council is therefore closely monitoring the

intensity and duration of the shock, as well as its indirect and

second-round effects," the ECB added.

Markets had seen just a one-in-five chance of another

interest rate hike at this meeting. They do, however, see a

four-in-five chance of a hike at the next one in September.

"The messaging remained unchanged and open," Morgan

Stanley's analysts said on the ECB's policy statement. "We

maintain our call for another rate hike in September, if energy

prices remain elevated."

In contrast to Europe's struggles, Asian markets had gained

overnight.

The KOSPI surged more than 4% in Seoul, led by 4.8% and 3.7%

respective gains for SK Hynix ( SKHY ) and Samsung

. Tokyo's Nikkei and Hong Kong's Hang Seng

also ticked higher.

But Wall Street futures pointed to a further dip there later

after results from Alphabet and Tesla - the

first two of the so-called "Magnificent Seven" megacap companies

to report this season - had failed to impress.

"U.S. megacaps may face more scrutiny because they are

writing the cheques, while chipmakers, memory suppliers and

infrastructure companies get paid earlier in the investment

cycle," Charu Chanana, chief investment strategist at Saxo in

Singapore, said.

YEN SLIPS BACK TO 40-YEAR LOW

In currency markets, the euro dipped back below $1.14

following the ECB decision having looked to be heading for a

one-week high earlier in the session.

Traders were now readying for ECB chief Christine Lagarde's

1245 GMT press conference and any hints she may give there.

As well as the oil price rise, scorching summer weather in

much of Europe this month looks set to hit harvests and push up

food prices, while low water levels on key rivers could create

awkward shipping bottlenecks.

Elsewhere, the Japanese yen was back at a 40-year low

versus the dollar as a brief lift, prompted by a Bloomberg

report on Wednesday that Bank of Japan officials were open to

raising rates at a faster pace, faded.

Japan's BOJ-sensitive 2-year government bond yield had hit a

31-year high in Tokyo on the oil moves and rate hike talk, while

Japan's finance minister had issued his latest verbal warning

about possible FX market intervention.

"The consensus view blames a timid BOJ (for the recent yen

fall), but I think the problem is that higher oil prices have

dashed hopes of 1.5% GDP growth this year," said Societe

Generale FX strategist Kit Juckes.

(Additional reporting by Ankur Banerjee in Singapore; Editing

by Joe Bavier and Andrew Heavens)