* Futures off: Dow 1.37%, S&P 500 1.48%, Nasdaq 1.87%

* Indexes set for biggest weekly jump in four months

* Globalstar ( GSAT ) jumps after report Amazon in buyout talks

(Updates before markets open)

By Purvi Agarwal and Twesha Dikshit

April 2 (Reuters) - Wall Street's main indexes were set

for a lower open on Thursday, in the last session of a

holiday-truncated week, after President Donald Trump signaled

more aggressive attacks on Iran, dampening expectations for a

swift end to the Middle East conflict.

During a closely watched address to the nation on Wednesday,

Trump said military operations would be intensified in the next

two to three weeks, in a sharp reversal from his earlier

comments that the U.S. will be "out of Iran pretty quickly".

Oil prices surged about 7%, taking Brent crude futures to

$108 per barrel. Energy stocks in the U.S. climbed, with Exxon

Mobil ( XOM ) and Chevron ( CVX ) up about 2.4% each in

premarket trading.

"The problem is that we didn't learn anything new. We're

back in a place where we know less, not more, about how we find

an off ramp to this war," said Art Hogan, chief market

strategist at B Riley Wealth.

"The market is going to retrace some of the constructive

action we saw over the last couple of days here."

Earlier this week, markets were optimistic that an end to

the war was near, putting Wall Street's three indexes on track

for their biggest weekly rise in four months, and the first week

of gains in six.

At 08:40 a.m. ET, Dow E-minis were down 641 points,

or 1.37%, S&P 500 E-minis were down 98 points, or 1.48%

and Nasdaq 100 E-minis were down 452.25 points, or

1.87%.

Futures tracking the Russell 2000 index fell 2.1%.

Wall Street's fear gauge, the CBOE VIX index rose to

27.54 points after falling to an over one-week low on Wednesday.

The month-long Middle East conflict battered global markets

in March, with the S&P 500 and the Nasdaq logging their

biggest monthly losses in a year, and Brent crude prices marking

their strongest monthly performance on record.

Money market participants are no longer pricing in any

easing from the Federal Reserve, per CME Group's FedWatch Tool,

as energy-driven inflationary concerns have clouded the central

bank's monetary policy outlook. They were anticipating two cuts

before the conflict began.

Investor focus will be on developments around Elon Musk's

SpaceX, which confidentially filed for a U.S. initial public

offering on Wednesday. The company is expected to target a $1.75

trillion valuation, according to a Reuters report, citing two

people familiar with the matter, which prompted a rally in

smaller peers.

Rocket Lab ( RKLB ), Planet Labs and Intuitive

Machines ( LUNR ) rallied on Wednesday in anticipation of

renewed investor interest in the space industry.

Meanwhile, data showed the number of new Americans filing

for unemployment benefits fell to 202,000 for the week ended

March 28, below estimates of 212,000, according to economists

polled by Reuters.

Nonfarm payroll numbers are expected on Friday, but U.S.

markets will remain closed for the Good Friday holiday.

Investors are also awaiting comments from Dallas Fed

President Lorie Logan later in the day.

In premarket moves, Globalstar's ( GSAT ) shares jumped

12.3% after a report said Amazon is in talks to buy the

low-earth-orbit communication satellites company.

(Reporting by Johann M Cherian, Purvi Agarwal and Twesha

Dikshit in Bengaluru; Editing by Mrigank Dhaniwala and Shinjini

Ganguli)