Opponents of President Gloria Macapagal Arroyo called for an inquiry Sunday into her role in a growing corruption scandal after she publicly acknowledged she allowed the signing of a major telecommunications contract after being warned of irregularities in the deal.

Arroyo admitted Saturday she was warned last April about possible corruption in the $330 million contract with Chinese telecommunications giant ZTE Corp., but said her government could not immediately back off from signing a deal.

Arroyo flew to China on April 21, 2007, to witness Chinese officials signing the contract, along with four other projects to be funded by China.

Five months later, Arroyo ordered officials to drop the deal after a losing bidder testified in the Senate that her husband and the then-elections chief had threatened him to make him abandon his bid for the national broadband project. Both men have denied any wrongdoing.

Arroyo's opponents say her statement and decision to scrap the project prove it was ridden with irregularities.

Arroyo did not say who told her about the alleged irregularities or specify what they were.

Arroyo said in a nationally televised speech after attending Mass Sunday that her government needed time to properly notify the Chinese government before deciding to cancel the ZTE contract. She added that she ordered two Cabinet members to study which agency should investigate an alleged bribery attempt in the ZTE project.

Opposition Sen. Aquilino Pimentel Jr. said he would urge Senate committees investigating allegations of corruption in the ZTE deal to look into Arroyo's statement and assess whether she violated anti-graft laws.

"What she said may be a smoking gun of her complicity," Pimentel told The Associated Press.

Another opposition senator and former national police chief, Panfilo Lacson, also sought an investigation of Arroyo and a number of Cabinet members, who may have committed perjury when they testified in the Senate that the ZTE contract was aboveboard.

Arroyo's statement that an abrupt cancellation of the project could affect ties with China was flimsy, considering national interest was at stake, Lacson said.

The scandal over the project has set off street protests, coup rumors and calls for the resignation of Arroyo, who has survived three impeachment bids and four attempted coups in her seven turbulent years in power.