Bill Gates's investment arm has
waded into a brewing takeover battle between Waste Management
(WMI.N) and Republic Services Inc (RSG.N), asking Waste
to walk away.

Just over a month after he left Microsoft Corp (MSFT.O),
Gates's BGI is lobbying the largest U.S. trash hauler to drop
the unsolicited $6.2 billion bid it made this month for
Republic, the third largest.

While his investment vehicles have stakes in dozens of
companies, they have kept low profiles over the years and Gates
has not traditionally been known as an activist investor.

But BGI didn't mince words in its letter to Waste
Management's CEO and board, disclosed on Thursday.

"We can only assume your ill-timed and poorly conceived
pursuit of Republic is designed to disrupt what you perceive as
a competitive threat to your position in the market," wrote
BGI, which manages Gates's investments and those of the $39
billion charity run by him and his wife.

"An acquisition of Republic will most certainly burden the
company with excessive debt, distract your management, result
in significant regulatory burdens, and thereby reduce
shareholder value," BGI wrote in the letter.

"We encourage you to act with the best interests of your
shareholders in mind, in a responsible and prudent manner, and
to abandon this acquisition."

Republic has already struck a deal to buy Allied Waste
Industries Inc
(AW.N) and rejected Waste Management's offer.

Cascade Investment LLC, Gates's investment vehicle, and
Bill & Melinda Gates Foundation Trust LLC together own about
2.3 percent of Houston-based Waste Management, which has grown
since the late 1960s into a trash hauler with more than 350
collection operations and 270 active landfill sites.

A call to a BGI spokesman late on Thursday was not
immediately returned.

Gates on June 27 said a teary goodbye to the company he
built into the world's most valuable technology company to
focus on his foundation, the world's largest charity, funded in
part by his vast fortune and that of his bridge buddy and
another multibillionaire, Warren Buffett.

The move by BGI follows efforts by fellow multibillionaire
and activist investor Carl Icahn to influence a six-month
takeover battle between Yahoo Inc (YHOO.O) and Microsoft.

Icahn is an activist shareholder in a variety of corporate
battles, seeking to boost investor returns at the companies in
which he has stakes.

(Editing by Braden Reddall)