* U.S. stock indexes mostly down slightly

* Oil prices gain as Iran worries continue

* Longer-dated U.S. Treasury yields off recent highs

(Updates to midday)

By Caroline Valetkevitch and Samuel Indyk

NEW YORK/LONDON, May 18 (Reuters) - Major stock indexes

mostly eased as technology shares fell on Monday, while oil

prices climbed following more worries over supply disruption

from the Iran war.

Longer-dated U.S. Treasury yields dipped after climbing to

their highest level in over a year in overnight trading.

Sovereign bond yields have risen sharply recently as

investors worry the war in Iran that began in late February may

bring a lasting inflationary shock.

Iran sent a new peace proposal to the United States with

terms that appeared similar to offers Washington has previously

rejected, although a senior Iranian official told Reuters on

Monday that the U.S. had softened positions on some issues.

A Pakistani source confirmed that Islamabad had shared the

latest proposal with Washington. But the source suggested

progress had been difficult.

U.S. crude was last up 1.32% at $106.81 a barrel.

Investors are focused on the tech sector's recent sharp

gains and are bracing for results from Nvidia ( NVDA ) this

week.

The tech sector, down 1.4%, led sector declines in

the S&P 500.

U.S. President Donald Trump's recent trip to China "left a

lot of open questions about the future of Taiwan and whether or

not the United States would be there to protect it," said Oliver

Pursche, senior vice president, advisor for Wealthspire Advisors

in Westport, Connecticut.

"Given Taiwan's significance to the chip market, that

partially explains the selloff we're seeing in that sector

today," he said, adding that investors are also taking profits.

Trump's first visit to Beijing since 2017 ended on Friday

with no major breakthroughs on trade or tangible help from

Beijing to end the U.S.-Israeli war on Iran.

The Dow Jones Industrial Average fell 4.47 points, or

0.01%, to 49,521.70, the S&P 500 fell 21.33 points, or

0.29%, to 7,387.17 and the Nasdaq Composite fell 171.47

points, or 0.65%, to 26,053.68.

MSCI's gauge of stocks across the globe fell

2.72 points, or 0.25%, to 1,096.28. The pan-European STOXX 600

index rose 0.54%.

Rising yields push up borrowing costs and mean a higher

discount for future company earnings, challenging stock

valuations.

The yield on benchmark U.S. 10-year notes dipped

to about 4.594% after hitting 4.631% in overnight trading.

Earlier, Japan's 10-year yield hit a peak not seen since

1996 as the government proposed to issue fresh debt to fund a

planned extra budget to cushion the economic blow from the Iran

war. Germany's 10-year bond yield rose to a

level not seen in 15 years.

AI, RETAIL EARNINGS TO TEST STOCKS' RECENT RALLY

The artificial intelligence trade will be tested by earnings

from Nvidia ( NVDA ) that are due on Wednesday, with

expectations sky-high for the world's most valuable company.

Nvidia ( NVDA ) shares are up sharply since a March low, while the

Philadelphia SE semiconductor index has also surged amid

demand for chips as tech companies spend massively to build

AI-related infrastructure.

Also due this week are results from a host of retailers,

including Walmart ( WMT ), which will provide an insight into

how consumers are faring with high energy prices.

The dollar slipped against most major currencies as U.S.

Treasury yields were off recent high levels.

The dollar index, which measures the greenback

against a basket of currencies including the yen and the euro,

fell 0.35% to 99.02.