"Now, we've updated the programme so that publishers can limit users to no more than five pages per day without registering or subscribing."
Google users may start seeing registration pages appear when they click for a sixth time on any given day at websites of publishers using the programme, according to Mr Cohen.
This will only affect websites that currently charge for content.
The announcement is seen as a reaction to concerns in the newspaper industry that Google is using newspaper content unfairly.
Media tycoon Rupert Murdoch, the chairman and chief executive of Newscorp, has accused firms such as Google of profiting from journalism by generating advertising revenue by linking readers to newspaper articles.
Some readers have discovered they can avoid paying subscription fees to newspaper websites by calling up their pages via Google.
Tim Weber, business editor, BBC News website
The dispute between media groups and Google reflects the general confusion over how traditional media can make money on the internet.
Every newspaper owner angry about Google's linking policy can use a simple remedy: add two lines of code to a file on your servers and Google will leave you alone.
Deep down, most media owners realise that the old "publish it and they will come" principle does not work in an on-demand world.
If Google would not link to their websites, the very same media groups would bitterly complain about Google's refusal to generate valuable online traffic.
Unless you own premium content (from the Wall Street Journal at one end to porn at the other), making money from on-demand content means first and foremost that your audiences have to be able to find you.
The problem: Nobody has quite figured out a business model for a world where consumers don't want their morning or evening news, but want the Now O'clock News - the "on-demand and to my taste" news.
This is because Google searches frequently link directly to newspaper articles, bypassing some sites' subscription systems.
Broadcasting and media consultant Steve Hewlett said that Google's response was "a pretty significant move".
"Rupert Murdoch is trying to build a consensus that paying for content online is right and that aggregators like Google that use newspaper content but don't pay for it are doing something wrong," he said.
Search for revenue
Newspapers are increasingly looking for new ways to make money from their online content amid a continuing decline in circulation figures and advertising revenues.
Earlier this week Johnston Press, the UK's largest regional newspaper publisher, announced plans to to begin charging for access to six of its titles online.
The move follows a 42% slump in advertising revenues at the group over the last two years.
Earlier this year, the Daily Mail and General Trust (DMGT) cut 1,000 jobs at its regional arm Northcliffe Media, which publishes more than 100 newspapers in England and Wales.
Newscorp, which owns the Times and the Sun newspapers in the UK, has also been affected by the downturn.
In June, it announced losses of $3.4bn (£2bn) for the previous 12 months, describing the year as "the most difficult in recent history".
It has also revealed plans to begin charging for access to all its online content. The corporation currently charges for access to its US title the Wall Street Journal.
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