* Indexes up: Dow 0.78%, S&P 500 0.87%, Nasdaq 1.29%

* Trump declares Iran ceasefire extension

* GE Vernova ( GEV ), Boeing ( BA ) and Boston Scientific ( BSX ) rise after

results

(Updates prices, adds analyst comment in paragraph 8)

By Avinash P and Niket Nishant

April 22 (Reuters) - Wall Street's main indexes climbed

on Wednesday after U.S. President Donald Trump extended the

ceasefire with Iran, even as uncertainty remained over whether

Tehran and U.S. ally Israel would honor the truce.

Trump said the indefinite extension of the ceasefire

followed a request by Pakistani mediators. However, the U.S.

Navy's blockade of Iranian ports remained in effect, and Iran

seized two ships in the Strait of Hormuz.

The opening of the waterway, responsible for about 20% of

global oil supply, remains a major unknown for investors and has

been one of the sticking points in the negotiations.

The bullish sentiment despite the uncertainty points to a

market desperate to cling to good news, and reflects investor

belief that despite setbacks, the war will be settled at the

negotiating table instead of the battlefield.

At 11:25 a.m. ET, the Dow Jones Industrial Average

rose 381.18 points, or 0.78%, to 49,530.56, the S&P 500

gained 61.56 points, or 0.87%, to 7,125.15 and the Nasdaq

Composite gained 313.74 points, or 1.29%, to 24,573.70.

"It's possible that we see a continuation of negative

headlines, ultimatums and deadlines for negotiations, but that

doesn't mean that stocks will react meaningfully to each one,

since markets already priced in the worst of the conflict during

the lows made back in March," said Rick Gardner, chief

investment officer, RGA Investments.

However, risks of an inflation flare-up remain, with oil

prices near the $100-a-barrel mark.

"Equity markets appear to be pricing in a rapid resolution

-- and conditions on the ground suggest that may be premature,"

said Larry Adam, chief investment officer at Raymond James.

Information technology stocks added 1.6% and were

the biggest boost to the S&P 500. Energy stocks also

rose 0.8%.

The Philadelphia SE Semiconductor Index hit a fresh

peak and was on track for its 16th straight day of gains -- its

longest streak ever.

Micron Technology ( MU ) shares jumped 5.6%, while Seagate ( STX )

rose 2.5% after Barclays upgraded the data storage

firm's rating to "overweight".

EARNINGS LIFT SENTIMENT

A strong run of earnings so far has reassured Wall Street

about the health of the U.S. consumer, the growth engine of the

economy.

S&P 500 EPS estimates for 2026 and 2027 have risen by 4%

since late January, according to data from Goldman Sachs.

GE Vernova ( GEV ) advanced 12.5% after the power equipment

maker raised its annual revenue forecast. Medical device maker

Boston Scientific's ( BSX ) shares were up 8.3% after

first-quarter results.

Shares of planemaker Boeing ( BA ) rose 3.1% after a

smaller-than-expected quarterly loss, and were among the biggest

boosts on the Dow.

United Airlines, however, declined 6.4% after

forecasting second-quarter and full-year profits below Wall

Street estimates as higher jet fuel prices squeeze margins and

cloud its near-term outlook.

EV giant Tesla, chipmaker Texas Instruments ( TXN )

and Southwest Airlines ( LUV ) will report after markets close.

Robinhood gained 2.3% after the retail trading

platform's venture fund invested $75 million in ChatGPT maker

OpenAI.

Shares of Spirit Airlines, which trades over the

counter, more than tripled to $1.85 following a Wall Street

Journal report that said the Trump administration was close to a

deal to rescue the embattled low-cost carrier.

Advancing issues outnumbered decliners by a 1.82-to-1 ratio

on the NYSE and by a 2.11-to-1 ratio on the Nasdaq.

The S&P 500 posted 29 new 52-week highs and one new low

while the Nasdaq Composite recorded 97 new highs and 40 new

lows.

(Reporting by Niket Nishant and Avinash P in Bengaluru; Editing

by Devika Syamnath)