The Tanaiste, Ms Harney, is to meet senior management of Apple Computers in the US this month, in an effort to persuade the firm to keep as many jobs as possible in Ireland.
It is believed the company wants to relocate its Cork printed circuit board factory to the Far East. Such a move would cost at least 100 permanent and 500 temporary jobs.
Another 400 jobs are at risk at Motorola's Dublin plant, the majority being workers employed on a casual basis assembling radio equipment.
Management's at both companies are currently implementing worldwide restructuring plans and want to cut back areas not central to their businesses.
In recent months Apple's workforce in Cork has grown to almost 1,900, some 900 of which are temporary jobs, not grant-aided by IDA Ireland.
The company's Irish operations became the centre of Apple's corporate strategy in April when the Cork plant was chosen to manufacture secretly the new Macintosh portable computer.
Until this year, Apple was losing hundreds of millions of dollars each financial quarter. The firm's new chief executive, Mr Steve Jobs, has returned it to profitability through continuing cutbacks and a refocusing of its products.
In January the company laid off 125 workers at a Dublin subsidiary, Claris Ireland.
In the long term, industry observers say, Ireland cannot hope to compete with low-wage, low-cost countries for jobs that do not require a high level of technical skills. The trend of shifting such facilities is set to continue, they believe.
Motorola, which issued a profits warning in March, has said it will cut 15,000 jobs worldwide because of weakening demand for its products.