LONDON, Aug 5 (Reuters) -

British scientific instruments maker Spectris ( SEPJF ) has

agreed to a sweetened offer from U.S. private equity firm KKR

valuing it at 4.8 billion pounds ($6.4 billion), it said

on Tuesday, withdrawing its backing for a lower offer from rival

suitor Advent.

The London-headquartered company said it had agreed to a

41.75 pound per share deal with KKR just four days after backing

a bid from Advent at 41 pound per share.

The two private equity firms have been vying for control

of the company for over a month after Spectris ( SEPJF ) agreed to an

initial offer from Advent in June.

Britain's subdued valuations and relative stability have

attracted overseas buyers, with a flurry of bids in recent

months highlighting appetite for UK assets.

The KKR offer values Spectris' ( SEPJF ) equity at 4.2 billion

pounds, with an enterprise value of 4.8 billion pounds.

($1 = 0.7528 pounds)