China-watcher Johnny Lau Yui-siu noted that the Communist Party had stressed Hong Kong's role in the "Greater China" concept, while messages about the city's democratic development were similar to what state leaders had said in the past.

The document emphasised the importance of deepening co-operation between the mainland, Hong Kong, Macau and Taiwan, as well as enhancing the role of Hong Kong and Macau in the country's economic development and opening up to the rest of the world.

The plenum also stressed the "One Belt, One Road" strategy, Beijing's push to drive cooperation among countries along the ancient Silk Road trading route to form a cohesive economic area.

The document highlighted mainland support for "developing the economy", "improving people's livelihoods", "promoting democracy" and "fostering harmony" in the two cities.

In September 2004, the fourth plenum of the Communist Party's 16th party congress stressed that maintaining long-term prosperity and stability in Hong Kong and Macau was a "brand-new subject".

The third plenum of the 18th party congress, in November 2013, mentioned the need for broadening cooperation with Hong Kong, Macau and Taiwan.

The central government's 12th five-year plan, from 2011 to this year, identifies Hong Kong as the "dragon head" of a regional financial system.

Lau said: "My reading is that the emphasis lies in Hong Kong's strategic role in cross-strait relations, rather than the city's democratic development." The language about democratic development was "not new and not different" from what state leaders had said before, Lau added.

"In the past, Beijing would not want Hong Kong and Taiwan, two capitalist entities, to get too close. But now it says the city should forge closer economic ties with Taiwan. Hong Kong's role will be to help pull Taiwan closer and eventually achieve the country's reunification."