Sadakazu Tanigaki, secretary-general of the ruling Liberal Democratic Party, has undergone surgery for a spinal injury in a cycling accident, the party announced Tuesday.

It remains unclear when he will be able to resume his duties, Hiroyuki Hosoda, acting secretary-general of the party, told a news conference at LDP headquarters in Tokyo.

Tanigaki's injury from the July 16 accident and his prolonged absence may cost him his senior position in the LDP during a shake-up of party executives and the Cabinet of Prime Minister Shinzo Abe slated for as early as Aug. 3.

While the accident was previously reported, the party did not admit that his injuries warranted surgery.

Tanigaki, 71, "suffered an injury to his cervical spinal cord after coming off a bicycle on July 16 and later underwent an operation," Hosoda said.

He added that the keen cyclist is making good progress: "He enjoys watching sumo on TV and remains lucid. There are no complications."

The LDP initially played down the severity of Tanigaki's condition, calling it "minor." But when he remained out of sight, people began speculating about his condition and rumors grew that Abe would remove him from his current position.

NHK reported Tuesday that while Abe has decided to keep Chief Cabinet Secretary Yoshihide Suga and Vice Prime Minister and Finance Minister Taro Aso in their respective roles, he will replace Tanigaki.

Abe did not speak about Tanigaki during an executive meeting at LDP headquarters Tuesday morning, Hosoda said, adding that Tanigaki himself has not said when he hopes to return.

Still, Hosoda voiced cautious optimism: "I think it's possible that he will soon be declared fine."