TOKYO, Aug 6 (Reuters) - Blackstone said on

Wednesday that it will launch a $3.5 billion tender offer for

TechnoPro Holdings ( TXHPF ), the Japanese engineer staffing

firm.

The world's largest alternative asset manager is offering

507.4 billion yen or 4,870 yen per a share - a 17.4% premium to

the share's closing average for the past three months.

TechnoPro ( TXHPF ) shares closed down 2% at 4,876 yen.

The Nikkei business daily reported the plan late on Tuesday,

saying Blackstone would offer a price below 4,900 yen.

($1 = 147.4600 yen)