Chile's Constitutional Tribunal again delayed a decision on a challenge to Chilean airline LAN's planned takeover of Brazil's TAM, a deal awaiting approval from the country's antitrust regulator.

After holding a hearing on Wednesday, tribunal officials said a decision on whether to formally take up a complaint by local airline PAL against LAN's LAN.SN planned takeover of TAM Linhas Aereas should be announced in the coming days.

"The decision on whether the complaint is taken up is pending and will be issued in the coming days," a tribunal official told Reuters. "There's no date yet."

The tribunal had already delayed making a decision last week.

Chile's antimonopoly regulator, TDLC, is probing the multibillion-dollar deal, which would create one of the world's biggest airlines, after a consumer group in Chile questioned it. It is widely expected to approve the takeover.

Shares of LAN were trading down 0.56 percent following the announcement, underperforming Chile's IPSA blue chip index .IPSA, which was up 0.6 percent in late Wednesday trade.

Shares of TAM were also trading down 0.42 percent, underperforming Brazil's benchmark Bovespa index .BVSP, which was up 1.33 percent.

In Brazil, the deal has cleared two of three antitrust hurdles and is awaiting action by the country's antitrust council, Cade.

LAN Chief Operating Officer Ignacio Cueto said this month he believed the takeover could be complete by the end of the year.