The Standing Committee of the National People's Congress on Wednesday approved a joint checkpoint for an express rail link connecting Hong Kong with Guangzhou and Shenzhen, marking key progress toward completing long-awaited infrastructure in the area.

The arrangement is in line with the Basic Law of the Hong Kong Special Administrative Region and the "one country, two systems" principle, the committee said.

It will enable Hong Kong and mainland customs and immigration clearance procedures to be conducted in one go at the West Kowloon terminus of the 142-km Guangzhou-Shenzhen-Hong Kong Express Rail Link, or XRL.

Customs and immigration officials from Hong Kong and the mainland will perform their duties at designated areas. The arrangement is crucial in increasing the efficiency and convenience of passengers boarding the bullet trains, and cutting their commute from the SAR to Guangzhou from two hours to less than 50 minutes.

Li Fei, deputy secretary-general of the NPC Standing Committee and chairman of the Hong Kong SAR Basic Law Committee, said the arrangement conforms to the Constitution and the Basic Law.

Li said he was impressed by the West Kowloon terminus when he visited in the past two months. The 400,000-square-meter terminus is an architectural success and should apply for the Guinness world record as the biggest underground railway station in the world, he added.

Eleven years ago, a similar joint checkpoint arrangement was adopted at Shenzhen Bay. Past experience has proved that using a joint location arrangement has solid legal basis and stands the test of time, Li said.

Construction of the XRL and the pending implementation of the checkpoint has shown the central government's unwavering support in incorporating the Hong Kong SAR into the country's overall development, Li said.

Huang Liuquan, deputy director of the State Council's Hong Kong and Macao Affairs Office, said the XRL was brought forward as part of plans to build a one-hour living, economic and intercity circle in the Pearl River Delta, with Hong Kong linked to the mainland's extensive high-speed railway network.

The arrangement is the most pragmatic and scientific solution to fulfill the original intent of the XRL to provide an efficient and convenient means of transport, Huang said.

After the NPC Standing Committee's decision, Hong Kong Chief Executive Carrie Lam Cheng Yuet-ngor said the SAR government will submit a draft to the city's legislature no later than February to set things on course to meet the planned opening of the XRL in the third quarter of 2018.

Lam said the arrangement arose from the implementation of "one country, two systems" and the decision by the NPC Standing Committee has given the plan a solid constitutional and legal basis.