Formed from a $500m joint venture unveiled only seven months ago, the new channel will attempt to challenge directly the primacy of Ted Turner's Cable Network News (CNN), which has had the field virtually to itself in 24-hour news programming since its foundation 16 years ago.
The birth of the new service, to be known as MSNBC, is likely to trigger a fierce battle in the industry for news viewers globally. Rupert Murdoch's Fox television company is also preparing to join the fray with its own all-news channel later this summer. Similar plans were recently shelved by ABC, owned by Disney, because of inflated costs.
MSNBC is attracting intense curiosity also because of its promise to fuse traditional television viewing with the Internet. An interactive version of the cable news service will be carried simultaneously on a World Wide Web site managed by Microsoft (http://www.msnbc.com.). Viewers will be encouraged to refer to the site for further details and context of individual news stories.
"Visionaries have said, 'Oh yes, some day the computer and the television screen will come together,'" commented Mark Harrington, the general manager of MSNBC. "Well some day turns out to be 15 July. What happens after that, we'll invent one day and one story at a time."
Executives have rushed to introduce the service in time to catch a peak period of news in the United States, beginning with the Olympic Games, which open in Atlanta next weekend, and the final stretches of the presidential campaign, which culminates with the election itself in November. President Bill Clinton is to be tonight's inaugural guest on Internight, an interview programme to be put out daily in evening prime time.
There will be nothing coy about MSNBC's determination to take on CNN, meanwhile. Several weeks ago, a giant billboard advertising the new venture was posted across the road from CNN's headquarters in Atlanta bearing the cheeky message: "The future of cable news from the people you know."
As its primary weapon, MSNBC has at its disposal not only NBC's 1,200- strong corps of journalists but also the network's most famous household names. Among these is NBC's veteran evening news reader, Tom Brokaw, who will conduct the interview with Mr Clinton.
CNN, meanwhile, has the advantage a world-wide brand identity for delivering round-the-clock news. Crucially, it also has a commanding presence on America's overcrowded cable distribution systems, with access to some 65 million US homes. To make way for the MSNBC, NBC is being forced to close down "America's Talking", an all-talk cable channel it launched two years ago. That service, however, has only made inroads into 16 million homes.
Finding space on cable is also a critical challenge for Fox. Rupert Murdoch recently offered cable operators $10 as a cash incentive for every viewer given access to his putative all-news service. It was that manoeuvre that persuaded ABC to throw in the towel. Even more strikingly, Mr Murdoch also last month offered Telecommunications Inc (TCI), America's largest cable operator, a 10 per cent stake in his new service in return for a guarantee that it would be automatically offered to TCI customers.
A danger for MSNBC, meanwhile, is that its launch may be coming too soon for the interactive side to be fully developed, which could lead to disappointment for users of the web. Technology that would allow full video of the cable news service to be played on the web is barely available yet and critics point out that CNN already has several web sites of its own. NBC executives predict, none the less, that within a few years more people will be accessing MSNBC by computer than on their televisions.