By Victoria Howley
LONDON (Reuters) - Advisers to AT&T and Deutsche Telekom's T-Mobile USA stand to lose $150 million in fees if the $39 billion deal collapses in what would be a massive blow to the increasingly fragile deals market.
The U.S. government has sued to block the bid, the largest since miner BHP Billiton's $43.2 billion offer for Potash was withdrawn, also in the face of political opposition, a year ago.
T-Mobile's advisers -- Deutsche Bank , Credit Suisse , Morgan Stanley and Citigroup -- and AT&T's banks -- Greenhill, Evercore and JP Morgan -- were on course to earn between $18 million and $36 million apiece before the intervention, according to estimates from ThomsonReuters/Freeman Consulting.
Growing economic uncertainty has already reduced the value of worldwide dealmaking to $180 billion in August.
That was the lowest monthly total since April 2010, threatening to reduce mergers and acquisitions revenue for the year by several billion dollars if transactions that were expected in January fail to emerge.
"This shows the severe execution risks M&A deals are facing currently," a senior investment banker close to the AT&T and T-Mobile deal said. "It takes much longer to close a deal and some companies won't even start to negotiate a merger due to these heightened risks."
Unlike its advisers, Deutsche Telekom will still get a windfall even if the deal collapses.
AT&T has promised to give Deutsche Telekom a break-up fee worth $6 billion, a record for a merger termination fee. The agreement includes $3 billion in cash, about $2 billion worth of spectrum and a roaming agreement valued at roughly $1 billion.
While the cash agreement is already unusually high at 7.7 percent of the total deal price, the addition of assets and services of a similar value would mean that the companies are breaking global records with a 15.4 percent break-up fee, according to Thomson Reuters data.
(Additional reporting by Philipp Halstrick. Editing by Robert MacMillan)