European officials on Tuesday agreed to a deal with the United States that would let Google, Amazon and thousands of other businesses continue moving people’s digital data, including social media posts and financial information, back and forth across the Atlantic.

With billions of dollars of business potentially at stake, the data-transfer deal was the result of more than three months of often tense negotiations between United States and European Union policy makers, who have clashed over what level of privacy individuals can expect when companies and government agencies follow ever-expanding digital footprints.

Part of the challenge is balancing individuals’ privacy concerns with national security obligations, particularly in light of mounting fears about international terrorism.

The agreement announced on Tuesday aims to address those privacy concerns and strike that balance by including written guarantees by the United States — to be reviewed annually — that American intelligence agencies would not have indiscriminate access to Europeans’ digital data when it is sent across the Atlantic. Whether that provision will reassure privacy-rights groups remains to be seen.