Top officials of five telecom carriers agreed Thursday to take on the government in a bid to nullify its approval of an increase in the interconnection fees the firms must pay when accessing NTT Corp. lines.

The lawsuit is expected to be filed July 17, followed by a joint news conference, officials of the five firms said.

KDDI Corp., Japan Telecom Co., Poweredcom Inc., Cable & Wireless IDC Inc. and Fusion Communications Corp. claim the telecommunications ministry's decision to allow NTT East Corp. and NTT West Corp. to raise fees by an average of 5 percent will severely damage their business.

On April 22, the Public Management, Home Affairs, Posts and Telecommunications Ministry announced the first interconnection fee increase since the introduction of the current fee system in 1994.

The ministry had tried to encourage competition among new telecom carriers through gradual reductions in NTT's interconnection fees.

But its about-face has fueled speculation the government is in bed with the telecom behemoth, industry officials said.