The U.S. stock market will open for a normal trading session on Monday, although with lower volume expected and some delays in opening hours, despite damage from Hurricane Irene.

The New York Stock Exchange, the Nasdaq Stock Market and the alternative BATS venue said they will start the week as usual. IntercontinentalExchange said Monday openings for some U.S. futures products will be delayed by one hour.

Subway service resumed at 6 a.m. on Monday, although Metro-North commuter rail service was still closed, stranding many who normally commute in from Connecticut and New York suburbs. So the city suspended for now, the question remains: How light will staffing be on Wall Street?

The decision to open the market was made early Sunday afternoon after regulators, exchange officials and others met to discuss the storm and market operations. The U.S. bond market will also operate as normal on Monday, the Securities Industry and Financial Markets Association said.

New York City regained limited bus service on Sunday evening and the PATH rail line that links New Jersey and Manhattan reopened early Monday.

Big trading firms Citigroup and Knight Capital both said they are ready to go Monday morning.

But a Bank of America Corp spokeswoman said the bank has not made a final determination on whether its operations will be open normally on Monday.

The storm has had little effect on the bank's downtown operations, but Bank of America was waiting word from New York city officials on when public transit will reopen.

Transit is the big question right now, she said.

The NYSE and broader U.S. marketplace are mostly automated, running quietly out of powerful data centers in New Jersey and elsewhere. Electronic trading is expected to function normally on Monday. But without full staffing, volume will take a hit.

This is a slow week anyway, and if anything this will just result in lessened volume, said Randy Billhardt, head of institutional sales and trading at MLV & Co in New York.

Hurricane Irene battered New York with heavy winds and driving rain on Sunday, knocking out power for some and flooding some of lower Manhattan's deserted streets, including in the Wall Street district.

Irene was downgraded to a tropical storm on Sunday morning as it sped northward but was still sending waves crashing onto shorelines and flooding coastal areas.

There was about a foot of water in the streets of the South Street Seaport in downtown Manhattan, although there was less damage than many had feared.

BACKUP PLANS

All of Nasdaq's trading members appeared to be ready to go for Monday, said Eric Noll, the exchange's executive vice president of transaction services.

Knight Capital Group, the top trader of NYSE-listed shares with 16.2 percent market share, said it would be fully operational.

Even in the event of a shutdown of our Jersey City campus -- if that were to occur -- we have redundancy built into our multiple trading desks, Peter Kenny, the firm's Jersey City-based managing director, said in an email. Our trading desk in Purchase, New York would act as our principle desk as Jersey City does on a day-to-day basis.

Our sales coverage and technology -- access to market -- will not be compromised on any level, he said.

The New York Mercantile Exchange (NYMEX), a few blocks from the NYSE, also plans at this time to open on Monday, parent CME Group Inc said on Sunday.

The NYSE trading floor now handles a fraction of the buy and sell orders it did five years ago, when about 3,000 brokers, specialists and others worked there.

There are now about 1,000 on the floor, and Lou Pastina, executive vice president of NYSE operations, estimated the Big Board would need half of them to open safely on Monday. Floor specialists are still important, particularly at the open and close of markets, when orders pile up.

Wall Street's biggest firms also said they weathered the storm well. Citigroup spokeswoman Danielle Romero-Apsilos said the bank's downtown buildings on Greenwich Street, which house its investment bank and other institutional client businesses, are fully functional, and employees can return when the city lifts its evacuation order for lower Manhattan.

The bank is looking at transport options for employees for Monday, pending updates on what will be happening with mass transit.

For staffers unable to report to their normal offices, Citi has alternative sites ready, and also offers employees remote access to company systems.

(Writing by Chris Sanders; Additional reporting by Ryan Vlastelica, David Sheppard, Joe Rauch, Dan Wilchins and Soyoung Kim; Editing by Braden Reddall and James Dalgleish)