NEW YORK (

TheStreet

) -- Ratings agency

Standard & Poor's

cut its rating of

Goldman Sachs

(GS) - Get Report

,

Bank of America's

(BAC) - Get Report

Merrill Lynch unit and

Citigroup

(C) - Get Report

long term debt from A to A-, and put their ratings on a "negative" watch, according to a statement issued after the market close Tuesday.

The new ratings were part of a sweeping change to its rating methodology for 37 financial institutions published on Nov. 9 . The changes also led to a

Wells Fargo

(WFC) - Get Report

downgrade from AA- to A+ and a

JPMorgan

(JPM) - Get Report

cut to A from A+, among a host of bank cuts spanning the world.

They include

Rabobank

of the Netherlands, which lost its vaunted AAA rating and mega-banks from Switzerland's

UBS

(UBS) - Get Report

, to Spain's

BBVA

(BBVA) - Get Report

and

Barclays

(BCS) - Get Report

of Britain among others.

For Goldman, Bank of America and Citigroup, the cut may prove to be costly. According to

Bloomberg

reports, Bank of America said in a November filing with regulators that if its rating were cut a notch, it would have to post $5.1 billion of additional collateral and other payments on its trades.

While Bank of America Merrill Lynch holds the same A- rating with S&P as competitors Goldman and Citigroup, Moody's holds its rating at Baa1 - below the A3 and A1 levels it ascribes to Citigroup and Goldman respectively.

Bank of America shares fell over 1% in afterhours trading after the company hit its 2011 low of $5.03 in Tuesday trading.

In its revised calculations, S&P raised its outlook on the ratings of

Credit Suisse

(CS) - Get Report

,

Deutsche Bank

(DB) - Get Report

and

State Street

(STT) - Get Report

from "negative" to "stable."

-- Written by Antoine Gara in New York