March 27 (Reuters) - U.S.-based Keysight Technologies ( KEYS )

is preparing to launch a formal offer for British

telecommunications testing firm Spirent Communications ( SPNUF )

worth roughly 200 pence a piece, Sky News reported on Wednesday.

The deal would be valued at about 1.15 billion pounds ($1.45

billion), the report added.

On March 5, U.S.-listed communications equipment firm Viavi

Solutions ( VIAV ) had agreed to buy Spirent for about 1.01

billion pounds. As part of the deal, Spirent shareholders would

get 175 pence per share.

The offer from Keysight ( KEYS ) represents an 84.5% premium to

Spirent's closing price of 108.40 pence on March 4, compared

with Viavi's premium of 61.4%.

Some institutional shareholders in Spirent had indicated

that they would vote in favor of Viavi's offer, but believed it

was opportunistic and left the door ajar for a rival bidder, the

Sky News report added.

Spirent Communications ( SPNUF ), Viavi Solutions ( VIAV ) and Keysight

Technologies ( KEYS ) did not immediately respond to Reuters requests for

a comment.

($1 = 0.7915 pounds)