SINGAPORE (Reuters) – A U.S. citizen, whose Singapore permanent residence status was revoked after the government identified him as being an agent of foreign influence, said on Tuesday he had appealed the decision to expel him.

The Ministry of Home Affairs said on Friday it had canceled the permanent residence of Huang Jing, a professor at Singapore’s prominent Lee Kuan Yew School of Public Policy, and of his wife, Shirley Yang Xiuping, also a U.S. citizen.

The ministry said Huang interacted with a foreign country with the aim of bringing about a change in the direction of Singapore’s foreign policy and that his wife was aware of his activities. It did not identify the foreign country with which he was said to be interacting.

Huang told Reuters on Tuesday that he and his wife have appealed the decision. He remains in Singapore.

“I did everything required by Singapore law and that’s all I can say,” Huang said. He declined to comment on the nature of the accusations against him.

The Ministry of Home Affairs last week said Huang and his wife could appeal, but if unsuccessful, would have to leave Singapore within a grace period.

The ministry declined to comment on Tuesday.