FILE PHOTO: A waitress issues a receipt at a cafe in Athens, Greece, June 25, 2015. REUTERS/Alkis Konstantinidis

BRUSSELS (Reuters) - U.S. financial services provider Fidelity National Information Services Inc (FIS) FIS.N is set to gain unconditional antitrust approval from the European Union for its $35 billion bid for payments company Worldpay WP.N, people familiar with the matter said on Monday.

The deal, announced in March, is the biggest in the fast-growing electronics payments industry which has seen a wave of consolidation recently.

FIS produces software for banks and asset managers as well as its financial services outsourcing business. Worldpay, spun off from Royal Bank of Scotland RBS.L in 2010, is a major player in card payments.

Global payments could top $3 trillion a year in revenue by 2023 as more people switch from cash to digital payments for online and in-store sales, according to consulting firm McKinsey.

The European Commission, which is scheduled to decide on the deal by July 5, declined to comment. FIS and Worldpay did not immediately respond to a request for comment.

FIS and Worldpay shares extended gains following the Reuters report. By 1445 GMT, FIS shares were up 2.5% and Worldpay up 3.9%.