BEIJING, April 22 (Reuters) - China on Tuesday defended a shipment of weapons headed for Zimbabwe as "perfectly normal trade" but said it may be heading back because the ship was unable to unload.

Zambia's president urged regional states on Monday to bar the An Yue Jiang from entering their waters, saying the weapons could deepen Zimbabwe's election crisis.

Chinese Foreign Ministry spokeswoman Jiang Yu said the contract for the shipment was signed last year and was "unrelated to recent developments" in Zimbabwe.

Zimbabwe announced a delay on Sunday in a partial recount of votes in March 29 parliamentary elections, extending a deadlock in which the opposition says 10 of its members have been killed and hundreds arrested.

The opposition says its leader Morgan Tsvangirai won presidential elections also held on March 29, and that President Robert Mugabe is attempting to cling to power by delaying declaring the result.

Jiang said the arms shipment was "perfectly normal trade in military goods between China and Zimbabwe", but because it was impossible for Zimbabwe to receive the goods, the company involved is now considering shipping the cargo back.

The 300,000-strong South African Transport and Allied Workers Union refused to unload the weapons because of concerns Mugabe's government might use them against opponents in the post-election stalemate.

Mozambique did not allow it to enter its waters.

For its part, China is trying to prevent the controversy from fuelling criticism over its human rights record and rule in Tibet ahead of hosting the Olympics in August. Sometimes-violent protests have followed the Olympic torch across the globe. (Reporting by Chris Buckley; Writing by Nick Macfie; Editing by Jerry Norton)

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