The United States on Tuesday insisted its food supply is safe and pork meat does not transmit the swine influenza virus.

"The American food supply is safe," US Trade Representative Ron Kirk and the head of the Department of Agriculture, Tom Vilsack, said in a statement.

"USTR and USDA are working closely with the Departments of Health and Human Services and the Centers for Disease Control and Prevention (CDC) to monitor the situation carefully," they said.

In their statement, Kirk and Vilsack cited references from the World Health Organization (WHO) and the CDC statements that there was no evidence of swine flu being transmitted by meat.

"Swine influenza viruses are not spread by food. You cannot get swine influenza from eating pork or pork products," the statements said. "Eating properly handled and cooked pork products is safe."

Stressing potential concerns about the safety of US pork and pork products, Vilsack stated that "while there is no evidence at this time that swine has been infected with this virus, the science is clear that consuming or handling pork, consistent with safe handling practices, is of no risk to consumers."

Kirk, the top US trade negotiator, urged all trading partners to base any food safety measures taken to protect their populations on scientific evidence and in accordance with their international obligations.

"Restrictions on US pork or pork products or any meat products from the United States resulting from the recent outbreak do not appear to be based on scientific evidence and may result in serious trade disruptions without cause," Kirk said.

The swine flu outbreak began in Mexico and has spread globally. The latest CDC data showed that there were 65 confirmed cases of human swine flu infection in the United States, none of them fatal.

In response to the outbreak, the WHO raised the worldwide pandemic alert level late Monday to Phase 4, signaling an increased likelihood of a pandemic.