UN agencies in the Philippines have written to President Benigno Aquino citing Manila's treaty pledge to ban tobacco advertising, promotion and sponsorship, World Health Organisation senior health adviser Eigil Sorensen said.
The ProTobEx Asia show, described on its website as featuring the latest innovations in processing, cigarette making and packaging, will be held at an indoor exhibition hall in the Pasay district of Manila from March 20-22.
"It's important that there is no official endorsement by the government of the tobacco event," Sorensen told AFP.
He praised the steps being taken by the Philippine government to curb tobacco use but said more needs to be done.
Sorensen noted that it was the second straight year that the Philippines was hosting the annual tobacco fair, which the WHO says gathers some of the world's biggest tobacco manufacturers and advertisers.
"If there is a government endorsement, it might be seen as a mixed signal," he added.
Sorensen took note of the significant reduction in the number of Filipino youth smokers, to one in 10 in 2011 compared to two in 10 four years earlier.
Last year the legislature passed a new law substantially raising tobacco taxes to help finance the government's health care programme.
However, Sorensen said 14 million Filipinos out of the nearly 100 million population smoked daily, leading to 10 deaths by the hour from tobacco-related diseases.
"Despite the significant decrease in the prevalence of smoking among youths 13 to 15 years old, the tobacco epidemic in the country remains a serious issue," Sorensen added.
"The Philippines has a vibrant tobacco industry. Tobacco has played, and continues to play, an important role in the domestic economy, earning millions of dollars for the country," the ProTobEx site said of the venue selection.
It praised the host city for lifting its blanket ban on indoor smoking at the trade show venue.
Organisers said the fair is not open to the general public or media.
Aquino spokesman Ricky Carandang did not immediately reply to the AFP's request for comment, while city officials were unavailable for comment.