Pacific Investment Management Co, the world's biggest bond fund, has seen assets under management exceed $1 trillion for the first time, underscoring investors' appetite for yield and portfolio diversification.

According to the Website of the Newport Beach, Calif.-based fund, which is run by founder Bill Gross, assets hit $1.0001 trillion as of the end of December, up from $941 billion at the end of the third quarter last year.

Even during the stock market rally last year, Gross saw his Total Return fund
become the top-selling mutual fund, with $199.4 billion in assets under management as of November 2009. Gross, who is co-chief investment officer at Pimco, saw his flagship fund begin 2009 at $132.3 billion.

Wednesday, mutual-fund tracker Morningstar named Gross its fixed-income manager of the decade, citing successful bets on mortgage-backed securities.

Gross and Mohamed El-Erian, who share the title of co-chief investment officer, recently tapped Neel Kashkari to head Pimco's investment initiatives, particularly in equities. Kashkari is a former Goldman Sachs banker who ran the government's $700 billion Troubled Asset Relief Program.

Gross and El-Erian are pushing to deepen the firm's products and services beyond fixed income, Pimco's bread and butter. They also hired Franklin Resource Inc's Anne Gudefin and Charles Lahr to boost Pimco's push into managing equities.

(Editing by James Dalgleish)