* Asset managers gain after labor department's 401(K)

guidelines

* Fed's Powell flags anchored inflation expectations

* Investors weigh Trump comments on Iran

* Indexes: Dow up 0.1%, S&P 500 down 0.4%, Nasdaq down

0.7%

(Updates close with volume, stock moves)

By Caroline Valetkevitch and Purvi Agarwal

March 30 (Reuters) - Major U.S. stock indexes mostly

fell on Monday as U.S. President Donald Trump's new warning to

Tehran and a widening of the Middle East war offset optimism

over his comments on U.S. discussions with Iran.

Trump said the U.S. was in serious discussions with a "more

reasonable regime" to end the war, but repeated his threat to

open the Strait of Hormuz or risk U.S. attacks on Iranian oil

wells and power plants. Iran described U.S. peace proposals as

unrealistic.

At the same time, the conflict has been escalating. Yemen's

Iran-backed Houthi militia entered the war over the weekend.

Investors have been rattled by uncertainties surrounding the

Middle East war, which has caused oil prices to spike and has

fanned inflation fears.

"The administration continues to send mixed messages," said

Rick Meckler, partner at Cherry Lane Investments, a family

investment office in New Vernon, New Jersey.

"When the messages seem good, to the extent they are

believed, it helps the market. If something they say implies a

more aggressive approach, the market sells off."

Meckler said investors may be looking for a technical

"bottom" after recent selloffs.

All three of the major indexes started the day higher after

logging sharp declines in the previous session. Since the war

started, the Dow, the Nasdaq and the small-cap Russell 2000

have all confirmed correction territory, ending 10% lower

from their record-high closes.

Technology stocks were among the day's biggest

drags on the S&P 500, with a semiconductor index falling

4.2%.

The Dow Jones Industrial Average rose 49.50 points,

or 0.11%, to 45,216.14, the S&P 500 lost 25.13 points, or

0.39%, to 6,343.72 and the Nasdaq Composite lost 153.72

points, or 0.73%, to 20,794.64.

Comments from Federal Reserve Chair Jerome Powell gave some

support to stocks. Powell said longer-term inflation

expectations appear to be holding despite the current energy

shock, and the Fed does not yet need to make a decision on how

to react to the latest troubles.

Money market participants have priced out any easing from

the Federal Reserve this year, compared with two cuts expected

before the war began, per the CME Group's FedWatch Tool.

The S&P 500 energy index ended down 0.9% even as oil

prices settled higher on the day. Brent crude is on

track for a record monthly rise and U.S. crude < settled

above $100 a barrel for the first time since 2022.

On the flip side, the financial index gained 1.1%

after the U.S. Department of Labor issued long-awaited

guidelines intended to clarify how trustees can add alternative

assets to 401(k) retirement plans.

Shares of asset managers climbed, with Blackstone

rising 3.3% and KKR gaining 2.1%.

Declining issues outnumbered advancers by a 1.14-to-1 ratio

on the NYSE. There were 147 new highs and 340 new lows on the

NYSE.

On the Nasdaq, 2,021 stocks rose and 2,794 fell as declining

issues outnumbered advancers by a 1.38-to-1 ratio.

Volume on U.S. exchanges was 18.85 billion shares, compared

with the roughly 20 billion average for the full session over

the last 20 trading days.