NTT Communications Corp. and Verio Inc. said Thursday that NTT Communications' planned purchase of a 90 percent stake in the Internet service provider poses no national security concern despite an ongoing investigation into the deal.

The two firms said they will continue to cooperate with the Committee on Foreign Investment in the United States during its investigation of the deal under the Exon-Florio Amendment to the Defense Production Act of 1950.

"Verio and NTT Communications continue to believe that the proposed transaction will be found to raise no national security concerns under the Exon-Florio law and that the Exon-Florio process will not prevent the parties from closing this transaction," the firms said in a joint statement.

NTT Communications, a unit of communications giant Nippon Telegraph and Telephone Corp., and Verio said they issued the statement in response to volatility in Verio's share price.

Under the Exon-Florio statute, which covers the investigative process, the CFIUS investigation will expire on or prior to Aug. 29, the companies said.

On May 7, NTT Communications, which already has a 10 percent stake in Verio, agreed to buy the remaining 90 percent to make it a wholly owned subsidiary.