(Bloomberg) -- Italy’s Nexi SpA and SIA SpA are close to clearing a major hurdle to a potential merger that would create one of Europe’s biggest payments providers, people familiar with the matter said.

SIA is finalizing an accord to keep Italian lender UniCredit SpA as one of its main clients, which has been a key sticking point in determining its valuation, according to the people. Extending the contract could pave the way for Nexi and SIA to reach a preliminary pact on a combination as soon as the next few weeks, the people said, asking not to be identified because the information is private.

Shares of Nexi have risen more than 20% in Milan trading this year, giving the company a market value of about 9.6 billion euros ($11.4 billion). Nexi and SIA are moving closer to an agreement on the pricing of a potential deal, though other terms of a transaction are still being discussed, the people said.

The companies have been weighing a combination on and off for more than a year, part of a trend of European payments providers seeking to bulk up. Combining the two Italian firms would create a stronger competitor to France’s Worldline SA, which agreed in February to acquire Ingenico Group SA in a 7.8 billion-euro deal.

The precise terms of UniCredit’s new contract with SIA will be key to assessing the payments company’s valuation, the people said. Negotiations are ongoing, and talks could drag on longer or fall apart, according to the people.

Representatives for Nexi, UniCredit, SIA and SIA’s controlling shareholder, state-owned Cassa Depositi e Prestiti SpA, declined to comment.

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