Speaking after the meeting, Yuen reiterated that both sides had agreed a single immigration checkpoint for passengers should be created, instead of checkpoints at each side of the border.

"The progress today is reasonably good. It's very constructive," he said. "We believe we should be in a position to achieve the target towards the end of 2017, when the railway is to start operation."

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Little progress has been made since the project received funding in 2010 amid legal and constitutional concerns that allowing mainland officers to work in Hong Kong would undermine the "one country, two systems" principle. The project was 68.7 per cent complete at the end of March.

Yuen said the aim was to achieve a consensus on the enforcement issue within the Basic Law, but declined to go into detail and said he did not want to see the project being politicised.

The two governments do not want checkpoints to be set up on each side of the border, as it would lengthen train journeys and defeat the purpose of building the express railway link to Guangzhou.

The MTR Corporation, which was entrusted by the government to build the HK$71.5 billion link, called on the administration to decide as soon as possible whether a joint checkpoint could be formed.

"From our project management perspective, the sooner that can be decided the better it is," MTR Corp chairman Dr Raymond Chien Kuo-fung said after yesterday's annual general meeting. But he said there was no deadline for the government to advise them of the arrangement.

Executive Council member and legislator Jeffrey Lam Kin-fun, of the Business and Professionals Alliance, dismissed concerns that allowing mainland officers to work in the terminus would pose a threat to the "one country, two systems" policy, as such arrangements worked in Western countries.

But Democrat Wu Chi-wai criticised his remark as "very inappropriate".

He said officials should not treat Hongkongers' concerns about the matter as merely the result of politicisation.

Legal sector lawmaker Dennis Kwok suggested that mainland immigration officials could conduct checks onboard cross-border trains, instead of setting up a joint border checkpoint in Hong Kong.

Speaking during an RTHK talk show on Thursday, he said this arrangement would involve mainland officials boarding trains in Hong Kong but only conducting checks after entering the mainland.

Speaking on the same programme, legislator Dr Priscilla Leung Mei-fun said his idea was "complicated". Supporting the joint checkpoint approach, she said Hong Kong should set up a "special zone" in West Kowloon for mainland officials to conduct border checks. 

She said this would not violate the Basic Law because Article 95 states that the judicial and law enforcement departments on both sides of the border can assist each other.

Leung said Hong Kong could take Canada as an example. Leung said the United States set up some pre-clearance counters at Vancouver’s airport for US-bound travellers. She said immigration checks were conducted under US laws at these counters. 

Dennis Kwok said however that Leung’s idea would undermine the Basic Law and would not solve contradictions between Hong Kong and the mainland’s different legal systems. 

He said mainland laws could be enforced in Hong Kong only in areas such as military and diplomacy and aspects in which the city is not empowered to handle. He said Hong Kong is allowed to control immigration to the city under the mini-constitution. 

The Basic Law Article 95 states that the Hong Kong Special Administrative Region may, through consultations and in accordance with law, maintain juridical relations with the judicial organs of other parts of the country, and they may render assistance to each other.

Joyce Ng, Timmy Sung, Jeffie Lam and Lai Ying-kit