Marconi is considering "all its strategic options" after its failure to land a major contract from BT.
In a move to reassure investors alarmed by the loss, the troubled telecome giant, which employs 1,800 people in Coventry, said that its annual revenues were still expected to top £1 billion, even excluding its business with BT.
"Customer interest in our next-generation equipment and services remains strong, with a number of orders already received," the company said.
Following the statement Marconi shares climbed seven per cent. However, it will heighten speculation that Marconi could put itself up for sale following the BT blow that wiped £500 million from its value.
Marconi added that it expected to announce the outcome of a headcount review "shortly" but did not provide further details.
Union leaders fear as many as 3,000 jobs could be lost as a result of BT's decision to award work to eight of Marconi's rivals - including Fujitsu in Birmingham - to equip a £10 billion development of its network.
Marconi, which has 30 per cent of existing business with BT, said: "The company clearly recognises the need to refocus its business in the light of BT's decision and recent trends in the global telecoms equipment market.
"The board will therefore continue to pursue all strategic options with the objective of maximising shareholder value."
The group added: " Management is reviewing the resource and headcount in each of its activities, particularly in the UK, and will announce shortly the result of this review together with the associated cost savings and level of headcount reduction."
Marconi pointed out that it continued to provide " worldclass equipment and services" to many of the world's leading telecom operators, adding that revenues excluding BT equipment and services were likely to top £1 billion in the year to the end of March this year.
It also has separate longterm contracts in place with BT.
Marconi will provide further details on trading on May 17, but said that revenues and operating profits for the final quarter of the financial year were in line with expectations. It also pointed out that it had £300 million of cash on its balance sheet.
Last week's announcement from BT represented a huge setback to Marconi, which had been showing signs of recovery following its life-saving financial restructuring in 2003.
It lost out in the bid process on price, even though chief executive Mike Parton said the products " performed extremely well technically".
Many analysts believe Marconi will have to put itself up for sale in order to gain the scale to compete effectively, although it could also consider partnerships with rival operators.
Marconi is no stranger to job cuts. It laid off thousands of employees as part of its recovery from a near collapse in the 2001 telecoms downturn.
It survived the previous downturn only after creditors agreed to forgive £4 billion in debt in return for 99.5 percent of its equity.
A spokesman said Mr Parton was due to meet Amicus union representatives today to discuss jobs at the company following the BT blow.
A union spokesman said: "We want to know why the company failed to win any of the work from BT and what the implications are for jobs and R&D.
"We also need to know what impact there will be on the pension scheme."
Marconi has already held discussions on the same subject with the Government, but the spokesman added that the company had not asked for any form of financial help.