WhatsApp is forcing users to agree to sharing information with Facebook if they want to keep using the service.
The company warns users in a pop-up notice that they "need to accept these updates to continue using WhatsApp" - or delete their accounts.
But Facebook, which owns WhatsApp, said European and UK users would not see the same data-sharing changes, although they will need to accept new terms.
The exception has been welcomed by some as a victory for EU privacy regulators.
The deadline in both regions to accept the change is 8 February, after which "you'll need to accept these updates to continue using WhatsApp", the company said in the pop-up alert to users.
Instead, the latest alert points users to its online help centre "if you would prefer to delete your account".
The move has prompted some people online - including Tesla and SpaceX founder Elon Musk - to call for users to switch to other more privacy-focused messaging services like Signal and Telegram.
There was initial confusion over how much the enhanced sharing of data would affect EU and UK users.
The "key updates" summary of important changes highlights integration with Facebook in the international copy - but does not do so on the European version of the same page.
Later on Thursday, Facebook issued a statement saying that there would be no changes in the "European region" - which covers the EU, EEA, and post-Brexit UK.
"For the avoidance of any doubt, it is still the case that WhatsApp does not share European region WhatsApp user data with Facebook for the purpose of Facebook using this data to improve its products or advertisements," a spokesperson said.
Facebook says it does not use WhatsApp information for those kind of purposes in Europe, because of negotiations with European data protection bodies.
Some held the development up as a success for Europe's tighter privacy regulations introduced in recent years.
Dutch MEP Paul Tang tweeted: "Facebook grants itself access to all of our WhatsApp-data unless…. you are living in the EU.
"That is why data protection matters."
What is collected elsewhere?
In an FAQ post, WhatsApp said it shares a wide range of user information with other Facebook companies, including:
- phone number and other information provided on registration (such as name)
- information about your phone, including make, model, and mobile company
- your IP address, which indicates location of your internet connection
- any payments and financial transactions made over WhatsApp
Facebook has not responded to a request for clarification on why it has made the sudden changes.