China is set to unveil this year the world's longest cross-sea bridge, connecting Hong Kong, Macau and mainland China.

The crossing, which took seven years to complete, is 55km-long and six lanes wide, comprising of of four tunnels and four artificial islands.

The multi-billion dollar project, which is being hailed as an international partnership, was reportedly built using more steel than 60 Eiffel Towers in the French capital, Paris.

"We have included a lot of foreign experts from the UK, US, Denmark, Switzerland, Japan, and the Netherlands," Gao Xinglin, Bridge team leader, told Al Jazeera. "They are from around 14 countries."

The bridge will cut travel time in half, drawing mainland China, Macau and Hong Kong to within an hour's commute of each other.

It has drawn criticism for over-spending and some fatal accidents.

However, Chinese authorities have hailed the finished project, inviting this week foreign media to inspect the crossing whose opening date has not yet been confirmed.

"We hope that the friends from the press can take this opportunity to see the new accomplishment of China in the new era and fresh progress of the 'one country, two systems'", Song Ruan, deputy commissioner at the Chinese Ministry of Foreign Affairs, told reporters at this week's

Hong Kong, a former British colony, returned to China in 1997 under a "one country, two systems" agreement that ensured its freedoms, including a separate legal system.

But Beijing has ultimate control, and pro-democracy protesters in Hong Kong contest it is increasingly clamping down on the city's constitutionally enshrined freedoms.

An estimated 40,000 vehicles a day are expected to use the new bridge, including shuttle buses running at 10-minute intervals.

The mega bridge is one of two major infrastructure projects set to open in the region this year - the other is a high-speed rail link to China.

"Both [projects] are being hailed as crucial transport links between the mainland and Hong Kong, but critics say it's another attempt by China to blur the border," said Al Jazeera Sarah Clarke, reporting from the Chinese city of Zhuhai.

The main criticism of the rail link is the plan to allow Chinese immigration facilities to operate in central Hong Kong, not on the border.

Some say this undermines Hong Kong's autonomy under the "one country, two systems" agreement.

"It's a kind of infrastructure telling the people of Hong Kong or the people on the mainland that Hong Kong and China are no longer two places," said Kwok Ka-Ki, Hong Kong's Civic Party lawmaker. "We are part of the mainland".

However, China says both multi-billion dollar transport projects will deliver Hong Kong more dividends with its integration, using one bridge to link three of the region's biggest economies.