The World Health Organisation on Wednesday said it was asking countries that took "significantly different" measures to combat swine flu, such as restricting international travel, to justify their actions.
"Countries adopting measures which are significantly different or which interfere with international traffic must provide WHO with the public health rationale and relevant scientific information for these measures," said Gregory Hartl, spokesman for the WHO.
Without specifying countries, Hartl added that the UN health agency had "begun the process of getting more information from a number of countries... on the public health rationale of their action".
Amid the influenza A(H1N1) scare, some countries, including Argentina, Cuba, Ecuador, Peru and China, have suspended flights from Mexico, the epicentre of the outbreak.
China's decision to quarantine Mexicans and suspend flights to and from Mexico has sparked a diplomatic uproar, with a chartered Mexican jet arriving in Beijing Wednesday to fly scores of its nationals home.
China has also banned imported pork from areas affected by swine flu, prompting a threat by Canada to file a complaint at the World Trade Organisation.
The WHO has reiterated that it advises no travel restrictions or border closures. It has also said that there is no risk of infection from the consumption of well-cooked pork and pork products.
Meanwhile, the WHO said the number of confirmed swine flu cases has climbed to 1,658, including 946 reported from Mexico.
Marie-Paule Kieny, WHO director of the initiative for vaccine research said vaccine manufacturers and experts will meet on May 14 to decide whether to ask the WHO to give the go ahead for the large-scale manufacturing of a vaccine against the influenza A(H1N1) virus.
Manufacturers should receive during the second week of May a so-called seed virus which is a precursor for the development and production of a vaccine against the flu, she added.
Addressing concerns that poor countries could be hit hardest by any pandemic due to their lack of infrastructure and resources to obtain necessary drugs, Kieny said the WHO is talking to manufacturers about procuring vaccines for developing countries.
"We hope that we'll be able in a few days, maximum a week, to announce that some agreement has been reached," she said.
She added that UN chief Ban Ki-moon, WHO Director-General Margaret Chan will meet drug manufacturers on May 19 to discuss "avenues to ensure more equitable access for developing countries to this vaccine when it is available".