* Futures down: Dow 0.45%, S&P 500 0.41%, Nasdaq 0.39%

* Marvell ( MRVL ) gains on report of deal with Google to develop AI chips

* QXO falls after $17 bln TopBuild ( BLD ) acquisition deal

(Updates before markets open)

By Purvi Agarwal and Avinash P

April 20 (Reuters) - Wall Street's main indexes were poised for a lower open on Monday

after a record rally on Wall Street last week, as renewed U.S.-Iran tensionsthreatened a

ceasefire and dented investor sentiment.

Iran's move to reopen the Strait of Hormuz on Friday helped fuel a broad market surge, with

the S&P 500 and the Nasdaq posting record highs for a third straight session and their biggest

weekly gains since May.

However, Tehran closed the waterway again after the U.S. said it had seized an Iranian cargo

ship that tried to run its blockade. Iran's foreign ministry said on Monday there were no plans

for a second round of negotiations with the U.S.

"One explanation for this diplomatic whiplash is the power vacuum at the heart of the

Iranian government. It may also be that both sides are increasing their leverage ahead of the

next round of talks while still fundamentally in search of a deal," said Lizzy Galbraith, senior

political economist at Aberdeen.

"Progress towards a lasting ceasefire and the reopening of the Strait of Hormuz, remains a

case of two steps forward, one step back."

Oil prices jumped 5% on Monday, lifting U.S. energy stocks higher in premarket trading.

Exxon Mobil ( XOM ) and Chevron ( CVX ) gained 1% each and Occidental Petroleum ( OXY ) added

1.7%.

Markets have been headline-sensitive of late, with even slight de-escalation leading to

improved risk appetite while investors turn cautious on escalation-linked news.

At 8:19 a.m. ET, Dow E-minis were down 223 points, or 0.45%, S&P 500 E-minis

were down 29.5 points, or 0.41% and Nasdaq 100 E-minis were down 105.25 points, or

0.39%.

The CBOE Volatility Index, known as Wall Street's "fear gauge", gained after falling

for the past eight sessions and was last up 1.79 points at 19.27, a one-week high.

Futures tracking the small-cap Russell 2000 index slipped 0.8% after the index

notched a record high on Friday.

Quarterly earnings will be in focus as investors wait to assess the impact of the Iran war

on corporate results and on the broader economy.

Defense giants Lockheed Martin ( LMT ) and RTX, alongside tech stocks such as IBM ( IBM )

and ServiceNow ( NOW ) are scheduled to report later this week. Tesla will kick

off results from the so-called "Magnificent Seven" cohort on Wednesday.

Data compiled by LSEG I/B/E/S expects first-quarter earnings from S&P 500 companies to grow

14.4%, compared with 13.7% a year ago.

Among premarket movers, Marvell Technology ( MRVL ) advanced 5% after The Information

reported on Sunday that Alphabet's Google is in talks with the chipmaker to develop

two new chips to run AI models more efficiently.

QXO shares dipped 2.1% after the construction supplies distributor struck a $17

billion deal on Sunday to acquire building products distributor and installer TopBuild ( BLD ),

whose shares jumped 19.5% on Monday.

Psychedelic drug developers gained after U.S. President Donald Trump signed an executive

order to speed up reviews and boost federal research funding.

Atai Life Sciences jumped 27% before the bell, while Definium Therapeutics ( DFTX )

added 14.5%, Compass Pathways ( CMPS ) climbed 26% and GH Research ( GHRS ) gained

19.6%.