The high-speed rail link to the mainland is by far the Mass Transit Railway Corporation's most significant project. Until it is completed, Hong Kong will remain isolated from the national grid, progress on the West Kowloon arts district will be hampered and our city's reputation for quickly constructing world-class infrastructure tested. Concern of yet another funding shortfall threatens further delays. Chief Executive Leung Chun-ying's call for problems to be swiftly dealt with so that the line can be finished as soon as possible makes the utmost sense. Construction difficulties have already pushed the completion date of the 26km line from this year to at least the third quarter of 2018. The cost has ballooned from HK$65 billion when work began in 2010 to HK$85.3 billion, 31 per cent more than the original estimate. There were bound to be unforeseen circumstances, with most of the track underground and a cavernous terminus in West Kowloon. But the corporation has given assurances and failed to meet deadlines. Leung was responding on Monday to Legislative Council transport panel chairman Michael Tien Puk-sun, who said the MTRC needed another HK$3 billion for the project, which is about 70 per cent complete. Without the extra funding, work may halt and there is a possibility contractors will seek compensation. Given the terms of the MTRC agreement, it is a matter of debate as to whether it or the public should pay. It is in Hong Kong's interests that the issue be promptly resolved. The MTR system has long been held up as a shining example of Hong Kong's ability to build and operate world-class infrastructure. Authorities logically chose the corporation to manage the high-speed rail project; its projections and schedule were approved and the government put up the funding. Delays and two requests for extra finance have been met, although each time with greater reluctance and scrutiny. Leung's demand shows that patience has worn thin. Five MTRC projects are under way in Hong Kong at present - the high-speed rail line is the most prestigious and, arguably, important. The corporation is experiencing management shortcomings, as evidenced by a series of service problems and delays to other construction schedules; Fred Ma Si-hang, who succeeds Raymond Chien Kuo-fung as chairman next year, has a tough job ahead. There is an obvious priority, though: getting the high-speed rail project back on track, and promptly.