Britain’s Prime Minister Boris Johnson said on Wednesday his country is ready to open the door to nearly 3 million Hong Kong citizens, as the leader of the Chinese semi-autonomous territory came to Beijing for meetings on a security law that it has made many worry about their future.

In a column published online by a Hong Kong newspaper, Johnson said the security law could limit freedoms in the city and conflict with China’s obligations under its deal with Britain to take control of the former colony. British in 1997.

“Many people in Hong Kong fear that their way of life, which China has promised to maintain, is threatened,” the British Prime Minister wrote in the South China Morning Post. “If China proceeds to justify its fears, then Britain, in good conscience, could not shrug and walk away.”

China surprised many of Hong Kong’s 7.5 million people by announcing in May that it would enact a national security law for the city, which is guaranteed a high level of autonomy except in foreign policy and defense.

Territory executive leader Carrie Lam, who supports the Chinese central government’s move, arrived in Beijing on Wednesday morning to meet with the executive about the new legislation. China could apply the new rule later this month or in late August, according to analysts.

About 350,000 Hong Kong citizens have a British passport, a legacy of the colonial era, and 2.5 million can apply for it, Johnson said in his column. The city’s DHL courier offices registered long lines as some have rushed to request or renew their documents.