By Tessa Walsh

LONDON (Reuters) - Belgian brewer InBev INTB.BR has launched a $45 billion (22.7 billion pound) syndicated loan backing its proposed buyout of U.S. rival Anheuser-Busch (BUD.N: Quote, Profile, Research), banking sources said on Friday, as the companies draw closer together.

InBev quashed queries over its financing by launching the loan, the second-largest European loan of the year after BHP Billiton's $55 billion deal, as it began negotiations with Anheuser-Busch on a friendly merger, a source told Reuters.

"We are not calling the bid hostile, it is unsolicited. There has been talk of a friendly deal which is what our M&A guys were expecting," a senior banker close to the deal said.

InBev is asking its relationship banks for large commitments of $1.75 billion each, in return for high pricing and fees and a rapid refinancing strategy, all of which have been designed to counter tough and illiquid loan market conditions.

"The company and its arranging banks have tried to eliminate all market risk," the senior banker said.

Around 20 senior lenders, in addition to the ten arranging banks, have been offered a generous initial interest margin of around 175 basis points (bps) over LIBOR stepping down over time to around 100 bps, sources said.

The pricing is among the highest seen on an investment-grade acquisition loan, and InBev is also offering high fees of 100 bps, several banking sources said.

"This is a must-do deal -- dealflow is limited and banks have budgets to make. This is as good a proposition as we've seen in investment-grade land," a banker close to the deal said.