Taking a step that has tempted and terrified much of the newspaper industry, The New York Times announced on Wednesday that it would charge some frequent readers for access to its Web site  news that drew ample reaction from media analysts and consumers, ranging from enthusiastic to withering.

Starting in January 2011, a visitor to NYTimes.com will be allowed to view a certain number of articles free each month; to read more, the reader must pay a flat fee for unlimited access. Subscribers to the print newspaper, even those who subscribe only to the Sunday paper, will receive full access to the site without any additional charge.

Executives of The New York Times Company said they wanted to create a system that would have little effect on the millions of occasional visitors to the site, while trying to cash in on the loyalty of more devoted readers. But fundamental features of the plan have not yet been decided, including how much the paper will charge for online subscriptions or how many articles a reader will be allowed to see without paying.

“This announcement allows us to begin the thought process that’s going to answer so many of the questions that we all care about,” Arthur Sulzberger Jr., the Times Company chairman and publisher of the newspaper, said in an interview. “We can’t get this halfway right or three-quarters of the way right. We have to get this really, really right.”