LISBON--Portugal Telecom SGPS SA on Monday postponed a shareholders' meeting to vote on the sale of its operating unit to France's Altice SA after the markets' regulator said holders lacked information on the deal.

The regulator, CMVM, said last week that it had asked Portugal Telecom several times since Dec. 22 to provide more details about Monday's meeting to approve the sale but hadn't received a response.

Portugal Telecom is in the process of merging with Brazilian phone company Oi SA. The combined group is planning to sell its operations in Portugal to Luxembourg-based Altice for 7.4 billion euros ($8.7 billion.)

Portugal Telecom said in a statement earlier Monday that it would release more information to the market sometime this week, adding that as a result, shareholders could decide to postpone Monday's meeting.

The holders later voted on the postponement to Jan. 22.

Portugal Telecom shares have been halted from trading since Friday.

Write to Patricia Kowsmann at patricia.kowsmann@wsj.com

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