Commenting on the row, the Chinese commerce ministry on Thursday praised the growth in economic ties with the US, but warned of "discordant notes" that it said threatened to undermine the relationship.
 
"The American media have been playing up the quality and safety issues of China-made products," it said, noting that the US congress had recently initiated 28 China-related trade and economic bills.
 
It called on both sides "to resist the negative impact of trade protectionism".
 
'Quality problems'
 
China is the world's largest importer of soya beans, but on Wednesday warned that inspections had found "numerous quality problems" in beans imported from the United States.
 
According to the General Administration of Quality Supervision, Inspection and Quarantine, the problems included adulteration with other beans, pesticides, harmful weeds and contaminated dirt found among the soya beans.
 
The allegations came on the same day that four US companies announced the recall of more than 300,000 China-made toys and nearly 22,000 pieces of children's jewellery, saying they contained potentially dangerous levels of lead.
 
The products include spiral-bound SpongeBob SquarePants stationery, spinning tops, as well as buckets painted with Thomas & Friends and Curious George and other toys and jewellery.
 
Lead poisoning can cause learning disabilities, behavioural problems, and, at very high levels, seizures, coma, and even death.
 
Under scrutiny
 
The recall came barely a week after US toy giant Mattel recalled nearly 20 million items around the world including dolls, cars and action figures, some of which were contaminated with lead paint.
 
Guangdong is home to many 
export manufacturers [Reuters]
The companies involved say no injuries have been reported from any of the recalled items so far.
 
The tainted toys are the latest in a list of Chinese exports that have come under scrutiny in recent months.
 
Products ranging from toothpaste to seafood to pet food ingredients have been found to contain toxic, illegal or excessive amounts of dangerous contaminants.
 
On Thursday, in an apparent response to the toy recalls, the state-run China Daily newspaper said toy makers in the southern province of Guangdong province will have to undergo "quality licensing" as part of a new inspection system.
 
"We will keep a closer watch on not only finished products but also on potentially dangerous chemicals and paints," an official with the Guangdong Entry-Exit Inspection and Quarantine Bureau was quoted as saying.
 
Guangdong, which borders Hong Kong, has long been a major centre of export manufacturing and is the location for hundreds of toy producers.