An EU watchdog said on Wednesday it needed time to study a new EU-U.S. agreement on data transfers to determine whether the United States was committed to limiting intelligence surveillance of Europeans.

Negotiators from the European Union and the United States agreed to the data pact on Tuesday. It will replace the Safe Harbor framework, which a top EU court ruled illegal last year amid concerns over mass U.S. government snooping.

“We want to receive the documents in order to assess whether this [newly agreed] EU-U.S. Privacy Shield can answer the privacy concerns raised,­” said Isabelle Falque-Pierrotin, chair of the WP29 grouping of data protection authorities.

WP29 only issues recommendations but it is influential because its members enforce data protection across the 28-nation EU and the bloc’s executive, the European Commission, has asked it to provide its expert guidance on the new pact.

Falque-Pierrotin said the group expected to have relevant documents by the end of February and to be able to reach a conclusion by the end of April. Pending its final verdict, some data transfers will not be allowed, she added.

Under the new Privacy Shield, the commission said U.S. companies would face stronger obligations to protect Europeans’ personal data, including limitations to U.S. surveillance programs.

The issue of data privacy has become politically charged in Europe since revelations by former U.S. National Security Agency contractor Edward Snowden that U.S. authorities had been harvesting private information directly from big tech companies such as Google and Amazon.

The WP29 group said intelligence services should respect four essential guarantees when dealing with data on EU citizens — clear rules on processing, access based on need and proportionality, independent oversight and effective remedies.

“We have concerns on the transfer regarding the scope of surveillance and particularly the remedies. The question is whether the [new] arrangement answers these concerns or not,­” Falque-Pierrotin said.

Many companies, both U.S. and European, used the Safe Harbor system to help them get around cumbersome checks to transfer data between offices on both sides of the Atlantic. That includes payroll and human resources information as well as lucrative data used for online advertising, which is of particular importance to tech companies.

(Reporting by Philip Blenkinsop; Editing by Gareth Jones)