Manchester United sponsor American International Group (AIG) is today preparing to launch a major restructuring effort to save its battered finances.

The global insurance giant is expected to announce an overhaul amid reports that it has asked the US Federal Reserve for a 40 billion dollar (£22 billion) lifeline.

AIG is the Premier League champions' main sponsor, having signed a four-year £56.5 million agreement in 2006 - the biggest shirt sponsorship deal in English football.

Man United said today it was "in close contact" with AIG, but declined to comment further.

AIG said it was reviewing its operations and looking at options with outside parties after shares plunged 45% on Wall Street last week amid concerns about the company's finances.

The group is reportedly looking for the Fed support after turning down private equity investment to retain control over its finances.

AIG is said to want the loan to rebuild its balance sheet, with aims to repay the debt through selling off assets.

AIG's chief executive, Robert Willumstad, who took the reins of the world's largest insurer in June, could announce a turnaround plan today involving the potential disposal of assets such as its aircraft-leasing business, according to reports.

The group employs around 3,000 staff in the UK out of some 116,000 globally.

It has 11 UK offices, including at Croydon, Reading, Bristol, Manchester and Glasgow.

AIG operates under three main brands in the UK - AIG UK, AIG Life and AIG Direct.

However, it also sells insurance through high street names such as Argos and Boots, while the firm underwrites product warrantees for John Lewis department stores.

AIG saw its former boss, British-born Martin Sullivan quit in June after a 36-year association with the insurer.

Mr Sullivan, who was raised in Dagenham, Essex and joined AIG as a 17-year-old clerk in the company's London office, ended his three-year tenure at the helm after facing calls to quit from shareholders.

He had overseen write-downs and losses of over 30 billion dollars (£16.8 billion), leading his predecessor and AIG's largest shareholder, Maurice Greenberg, to speak out against Mr Sullivan.

The group's latest crisis comes as it is also threatened with a credit ratings downgrade from Standard & Poor's - news which sent the group's shares down 30% in US trading on Friday alone.