Thousands of tons of rotting watermelons are stuck at a border checkpoint between Vietnam and China, because of new quotas from Beijing.

Tons of fruit are rotting at Long San border crossing, one of Vietnam's busiest gateways into China. More than 300 trucks filled with watermelons have been held up at the border because of new quotas aimed at protecting Chinese farmers.

The fruit restrictions went into effect without warning three weeks ago, and soon the watermelon pileup began. For Vietnamese farmers, the holdup means a loss of income in one of its most lucrative markets. Each large truck represents about $1,000 to farmers and traders - more than a year's income for most Vietnamese.

Vietnamese officials say China is trying to protect farmers on Hainan Island, who in recent years have faced new competition from Vietnamese watermelons.

Beijing and Hanoi are negotiating the quotas, and Chinese officials on Tuesday agreed to let about 100 trucks pass through the Long San checkpoint. But that is still less than half the normal flow of fruit over the border.

Once regional political rivals who fought a brief border war in 1979, China and Vietnam have more recently become trade partners. Trade between the two communist countries reached almost $3 billion last year. Officials have set a goal of $5 billion in trade within three years, despite lingering issues such as watermelons.