And the slowdown is not limited to Shenzhen. Shanghai, the mainland's largest port, also saw growth cut to a single digit in May, when it posted an 8 per cent increase in throughput.

Analysts say a complex set of factors are to blame: the economic slowdown in the US, a cut in the across-the-board export tax rebate, yuan appreciation and changing labour laws. All have left the export and import-oriented terminals fighting a hard battle to maintain growth.

Analysts said Yantian port, controlled by Hutchison Whampoa, was being especially hurt by a weakening US economy, since about 70 per cent of its shipping line customers served the transpacific trade.

The slump at Yantian has proved a drag on the entire Shenzhen port system, which consists of Yantian in the east and Shekou and Chiwan ports in the west. Together, they serve as the gateway for merchandise from the Pearl River Delta to the world.

Shenzhen, the second-busiest port on the mainland, saw growth halved to 7 per cent in the first half, down from 14 per cent on average last year, Ma Yongzhi, a vice-director general of the Bureau of Communications of Shenzhen said yesterday in Changsha, Hunan.

The slowing trend is likely to continue.

'The risk is building for next year when manufacturers negotiate new contracts with importers from the west,' said Geoffrey Cheng, a transport analyst for Daiwa Institute of Research.

'Owing to rising costs and an appreciating yuan, some factories may trim their exporting contract volume, which will lead to further declines in throughput growth next year.'

However, ports in Shenzhen west still maintained strong growth in the first six months with a 20 per cent increase in container throughput, said a manager from China Merchants International, which operates the ports in the west.

The ports' even distribution of routes - calling on European, US and Asian destinations - has helped the firm defy weakening US demand. Shekou handled 34 per cent more containers in the first five months.

'We are looking at attracting more domestic shipments to Shenzhen to reduce the impact from the export slowdown,' Mr Ma said.

In the past, Shenzhen has been too occupied with international direct cargo, allowing much of the domestic cargo to go to neighbouring ports such as Nanshan.

Mr Ma said the port had decided to adjust its strategy to increase the proportion of domestic cargo.

A proposal is being examined by the Shenzhen municipal government to change the proposed Da Chan Bay Terminal phase three into a feeder port for domestic shipments rather than a bulk port as suggested in a previous study.

The new phase would help the first two phases in Da Chan Bay, which have just come on stream this year, to cater to more domestic shipments.

However, from a port operator's point of view, domestic shipments are less attractive because rates are less than half those levied on international shipments, according to industry sources.