GUANGZHOU, March 7 (Xinhua) -- The last pipe was put in place on Tuesday, as work on the undersea tunnel of world's longest cross-sea bridge, linking Zhuhai in Guangdong Province with Hong Kong and Macao, nears its end.

The 5,664-meter tunnel, believed to be world's longest sunken pipe tunnel, comprises of 33 sections. and is now 12 meters from closure. Construction of the bridge began in December of 2009 in Zhuhai.

The bridge and tunnel system spanning the Pearl River estuary is an important waymarker in the integration of Hong Kong, Macao and Guangdong. The Y-shaped bridge starts from Lantau Island in Hong Kong with branches to Zhuhai and Macao.

Major construction work on the 55-km bridge was completed last September. It is expected to be open to traffic by the end of this year.

Once in operation, the current four-hour drive from Hong Kong to Zhuhai will be reduced to less than an hour. All Pearl River Delta cities will then be within a reasonable commuting radius of Hong Kong.