The US defence giant Northrop Grumman has launched a hostile takeover bid for TRW, valuing the company at $5.9bn (�4.1bn).

If the bid succeeds, Northrop Grumman plans to spin off TRW's automotive business. The combined defence and aerospace business resulting from the takeover would have a combined turnover of about $27bn.

"We believe the strategic combination of Northrop Grumman and TRW will provide tremendous value to the shareholders of both companies," said Kent Kresa, Northrop Grumman's chairman and chief executive.

At TRW, executives said they would examine the offer, but called its timing "regrettable". TRW's share price is currently in a slump, following the recent unexpected departure of the firm's chief executive David Cote.

In a statement, TRW said its current share price was "aberrationally low".

Northrop Grumman is famous for its cutting edge avionics knowledge, producing plans like the bat-winged B-2 stealth bomber.

The firm also gained prominence with its Global Hawk reconnaisance aircraft, an unmanned spy plane that can stay in the air for long distances and many hours. Most recently the plane was used over Afghanistan to hunt for Osama bin Laden.

Missiles defence

Northrop Grumman is likely to be one of the top contributors to the planned national missile defence system envisaged by US President George W Bush.

Mr Kresa said "Northrop Grumman's electronics and systems integration capabilities, combined with TRW's space and systems expertise, would create a strong contributor to the nation's satellite and missile defence requirements."

Northrop has said it is offering $47 in stock for each TRW share.

In November, Northrop took over the nuclear aircraft carrier Newport News Shipbuilding in a deal worth $2.1bn.

In 1998 Northrop tried to merge with its rival Lockheed Martin, but the deal was blocked by the US government.

The firm's nearly 100,000 employees generate sales of military and aerospace equipment worth $18bn.

Northrop's headquarter is in Los Angeles, and the firm has worldwide operations in 25 countries.

TRW is a specialist in aerospace products and services, information systems and automotive markets, with annual sales of $16.4bn.

TRW acquired its automotive business in 1999 when it bought Lucas Varity, the UK car parts maker.