TOKYO, Jan 13 (Reuters) - Japan"s Hitachi Ltd will sell about half its 51% stake in unit Hitachi Construction Machinery Co to trading firm Itochu Corp (8001.T) and investment fund Japan Industrial Partners, public broadcaster NHK reported on Thursday. Hitachi will sell the stake for about 200 billion yen ($1.7 billion), according to a Nikkei business daily report, which did not identify the source of the information. The construction unit"s market value at the end of share trading in Tokyo was 753 billion yen. The sale would represent the final tranche of Hitachi"s decade-long business portfolio overhaul, following sales of chip-making equipment manufacturer Hitachi Kokusai Electric and chemicals maker Hitachi Chemical. "We are considering various ways improve corporate value, but we have no decision yet," Hitachi said, when asked about the NHK report. Hitachi Construction, the smaller rival of Komatsu Ltd (6301.T) and Caterpillar Inc (CAT.N), generated 813 billion yen ($7.1 billion) in its last full business year from sales of excavators, wheel loaders, dump trucks and their parts. It employs about 25,000 people worldwide with about three-quarters of sales outside Japan. ($1=114.6200 yen)