UPDATE 1-Olympics-2012 chiefs in talks with struggling Nortel

(adds Nortel statement, para 5-6)

LONDON Jan 15 (Reuters) - London 2012 Olympics organisers said on Thursday they were in talks with Games sponsor Nortel after North America's biggest maker of telephone equipment filed for bankruptcy.

As a Tier One sponsor, Nortel is contributing around 40 million pounds ($58 million) to the 2012 organising committee's kitty as well as supplying some of the communications infrastructure to the Games.

The organising committee (LOCOG) has already raised around 400 million pounds from private sector sponsorship but Nortel's problems will fuel fears that the global economic downturn could make it more difficult to meet its 1 billion pounds target.

"We are talking to Nortel. We are aware of the situation and will work through it with them," a LOCOG spokesman said, adding that the company had met all its obligations to London 2012.

In a statement on Thursday Nortel reaffirmed its commitment to the London 2012 Olympics.

"Our commitment to the Games as a Tier 1 local sponsor and official Network Infrastructure Provider remains unchanged as does our commitment to all our customers," the statement read.

Nortel, which filed for bankruptcy on Wednesday, is also a main sponsor and supplier for the 2010 Winter Olympics in Vancouver. Officials said on Wednesday that the Canadian company had also reaffirmed its commitment to those Games.

LOCOG has been pleased with its progress in attracting sponsors, saying it was ahead of schedule compared to previous Olympics. British Airways, sportswear firm adidas, BT, EDF Energy and Lloyds TSB bank have all signed up as Tier One sponsors.

However, LOCOG chief executive Paul Deighton said recently that the harsh economic climate could make things more difficult.

"Over the next 12 to 18 months it is bound to get a little bit tougher," Deighton said when chocolate company Cadbury were signed up as a 20 million pounds backer in October.

There was better news for LOCOG on Thursday when The Boston Consulting Group was signed as the first Tier Three sponsor for the Games, providing strategic support.

On Wednesday recruitment firm Adecco signed up as a Tier Two partner, bringing an estimated 20 million pounds to the table. (Reporting by Martyn Herman; Editing by Sonia Oxley)