Biggest bank deal ever: What to watch

NEW YORK (CNNMoney.com) -- Dutch bank ABN Amro agreed Monday to be bought by British bank Barclays in a deal valued at $91 billion, which would be the biggest deal ever in the financial sector.

The companies say they expect the deal to close in the fourth quarter, but it could run into some obstacles. Here's a look at what U.S. investors should be watching and how the deal affects them:

Rival bidders circling. A rival group of suitors led by Royal Bank of Scotland has its eyes on ABN Amro. The group, which includes Spain's Santander Bank and Dutch-Belgian company Fortis, was set to meet with ABN Amro Monday but canceled the meeting to consider the Barclays offer and ABN's decision to sell LaSalle Bank.

The acquisition of Chicago-based LaSalle was considered to be a big draw for Royal Bank of Scotland, since it would provide access to the U.S. market. Despite the sale of LaSalle, some analysts weren't ruling out the possibility of a bid from the Royal Bank of Scotland group.

"The sale of LaSalle to potentially the highest bidder (BoA), may weaken the RBS buy case; however, we believe RBS will continue to formulate an offer once it has had time to digest the Barclays offer terms," Keefe, Bruyette & Woods analysts in London wrote in a note Monday.

Boost for Bank of America. ABN Amro will sell its U.S. unit, LaSalle Bank, to Bank of America (Charts, Fortune 500) for $21 billion as part of the agreement with Barclays.

The move could help Bank of America gain an edge in Chicago, the third-largest banking market in the U.S., against rivals like JP Morgan Chase (Charts, Fortune 500). LaSalle has about $113 billion in total assets and operates 141 offices in the Chicago area.

Bank of America has been in Chicago for some time, but hasn't been able to develop the market, according to Friedman, Billings, Ramsey analyst Gary Townsend. "It's a very desirable franchise," he said of LaSalle. "This instantly makes them large [in Chicago]."

Investors appeared to express some concern about the hefty price tag. Bank of America shares slid 1 percent in midday trading Monday.

Competition heats up. Consolidation in the banking sector has been going on for years in the United States, but the ABN Amro deal represents a new wave of dealmaking in Europe - and more deals are likely to follow on its heels.

"As the financial business becomes more global and requires more scale to compete for certain transactions, I would expect deals to continue as they have been for the past couple of decades," said Edward Keon, chief investment strategist at Prudential Equity Group in New York.

As more deals occur in Europe, U.S. banks could feel the pressure on their global business. U.S. banks seeking growth have been on a drive to expand overseas. Earlier this year, Citigroup (Charts, Fortune 500) announced it would buy UK online bank Egg for about $1.1 billion to broaden its reach in the U.K.

A fight from shareholders. The Barclays-ABN deal could meet resistance from some shareholders looking for an even sweeter offer, especially from The Children's Investment Fund (TCI), a London-based hedge fund.

TCI has put forth motions proposing the sale or break-up of ABN Amro. Those proposals will be voted on at ABN Amro's annual shareholder meeting on Thursday. While ABN Amro has addressed some of TCI's concerns by agreeing to the deal with Barclays, the company prefers to be sold as a whole, analysts say.

ABN Amro could face pressure to explore bids that call for its operations to be split up and sold off. Some analysts say such a break-up could result in more cost-savings and better return for shareholders.