A mainland legal expert told the people of Hong Kong on Wednesday to maintain confidence in the "one country, two systems" principle even as the city faces its biggest challenge in the 22 years since its return to the motherland.

Problems can be solved as long as every sector in the city faces up to the challenges, respects the Constitution, and conducts constructive dialogues in legal and peaceful ways, said Han Dayuan, a member of the Hong Kong Basic Law Committee of the National People's Congress Standing Committee.

Han made the remarks during his keynote speech at the city's third National Constitution Day forum at the Hong Kong Convention and Exhibition Centre.

"We should not cast doubts on the 'one country, two systems' principle, nor should we lose confidence in it," said Han, who is also dean of the School of Law at the Beijing-based Renmin University of China.

"One country, two systems" is an arrangement created by the Chinese people to realize the peaceful reunification of the country, which reflects the wisdom and rationality of the Chinese people, Han said. "We need to protect it," he added.

At the same time, Hong Kong needs to reflect on the problems it has faced since its return to China — particularly those issues that have been exposed in nearly six months of violent protests that have challenged the "one country, two systems" principle.

Han said he agrees with Chief Executive Carrie Lam Cheng Yuet-ngor that the city's civil servants and young people should enhance their understanding of the national Constitution and the Basic Law through education.

Responding to a student's question about the "expiration date" of the "one country, two systems" principle, Han said that stipulation of the Basic Law is open-ended.

According to Article 5 of the Basic Law, the socialist system and policies shall not be practiced in Hong Kong, and the city's capitalist system and way of life shall remain unchanged until 2047.

Han said he personally sees no reason to change the "one country, two systems" principle after that.

The "one country, two systems" principle is also a contribution to a global political civilization, Han said. "Being responsible for a global civilization, we have every reason to improve it," Han told the forum.