* Indexes down: Dow 0.45%, S&P 500 0.77%, Nasdaq 1.05%

* Meta Platforms ( META ), Alphabet fall after US jury verdict

* OECD warns Iran war erases global growth upgrade

* Weekly jobless claims in line with estimates

(Updates with afternoon prices)

By Twesha Dikshit and Purvi Agarwal

March 26 (Reuters) - Wall Street's main indexes dropped

on Thursday following gains in the previous session, as

conflicting signals from the U.S. and Iran on the prospects of a

de-escalation in the Middle East kept investors on edge.

A U.S. proposal for ending nearly four weeks of fighting is

"one-sided and unfair", a senior Iranian official told Reuters

on Thursday, while also stressing that diplomacy had not ended

despite the current lack of a realistic plan for peace talks.

"There's just a lot of confusion as to what is really

happening. Is the administration negotiating with Iran or

there's just confusion around that? That's why you're seeing

this back and forth," said Hank Smith, director and head of

investment strategy at Haverford Trust.

"But the market has held up really well partly because there

is a fear of missing out on a rebound when the war ends."

At 12:00 p.m. ET, the Dow Jones Industrial Average

fell 202.81 points, or 0.45%, to 46,221.54, the S&P 500

lost 50.27 points, or 0.77%, to 6,540.93 and the Nasdaq

Composite lost 229.53 points, or 1.05%, to 21,700.29.

Jurors in the first two trials from a growing wave of

lawsuits targeting social media firms over harm to children have

found Meta and Alphabet's Google liable,

sending their shares down 6.3% and 2.1% respectively, to

multi-month lows.

They bogged down the S&P 500 communication services index

by 2.4%.

Technology stocks were the biggest weights on the S&P 500

, falling 1.2%. Memory chipmakers continued to sell

off, with Micron Technology ( MU ), SanDisk ( SNDK ) and Western

Digital ( WDC ) down between 4% and 7%. The Philadelphia SE

Semiconductor index lost almost 2.7%, after three

sessions of gains.

The escalating conflict in the Middle East has knocked the

global economy off a stronger growth path, the OECD warned on

Thursday, with a closure of the Strait of Hormuz threatening to

push inflation sharply higher.

Oil prices rose by over 4% on the day, making the S&P 500

energy sector the biggest percentage gainer on the

benchmark index.

Central banks have been put in a tough spot with regard to

interest rates, as money market participants no longer price in

any easing from the U.S. Federal Reserve this year. Two rate

cuts had been expected before the Iran conflict erupted,

according to the CME Group's FedWatch Tool.

Data showed new applications for U.S. unemployment benefits

rose slightly last week, suggesting a stable labor market and

allowing the Fed to hold rates steady while monitoring the

impact of the Iran war.

Comments from Fed officials Lisa Cook, Stephen Miran,

Michael Barr and Philip Jefferson are on deck through the day.

Among individual movers, shares of Olaplex ( OLPX ) jumped

51% after Germany's Henkel agreed to buy the hair-care

brand in a $1.4 billion deal.

U.S.-listed shares of gold miners slipped as bullion prices

declined more than 1%. Sibanye Stillwater lost

1.7% and Harmony Gold shed 1.9%.

Declining issues outnumbered advancers by a 1.74-to-1 ratio

on the NYSE and by a 1.44-to-1 ratio on the Nasdaq.

The S&P 500 posted 17 new 52-week highs and five new lows,

while the Nasdaq Composite recorded 39 new highs and 103 new

lows.