The UK-based payment processor WorldPay is being purchased by its US rival in a deal worth $43 billion.

Fidelity National Information Services (FIS) will pay $35bn in cash plus shares, and also take on WorldPay's debt.

WorldPay was sold by Royal Bank of Scotland (RBS) as part of its government bailout following the financial crisis.

Gary Norcross, FIS chief executive, said: "The need to invest, to continue to modernise both the technology and application layers, and continue to innovate so our customers can continue to be disrupters, will be important for us."

He added that "scale matters in our rapidly changing industry".

FIS said that purchasing WorldPay would help it to sell services to banks and financial firms.