The US will extend a public transportation mask mandate for 15 days while the country’s top public health agency monitors a recent rise in coronavirus cases.

The federal mandate, which requires travellers on public transport including aeroplanes, trains and buses to wear masks, was set to expire on April 18.

“In order to assess the potential impact the rise of cases has on severe disease, including hospitalisations and deaths, and healthcare system capacity, the CDC order will remain in place at this time,” the US Centers for Disease Control said.

“The Transportation Security Administration has decided to extend the security directive and emergency amendment for 15 days, through May 3, 2022,” the CDC continued.

The public health agency also said it would change its alert system for international travel, so travellers will only be warned to avoid visiting a country in extraordinary circumstances, such as the emergence of a dangerous new variant, rather than anywhere where the spread of Covid-19 is deemed very high. This Level 4 category currently applies to a wide list of countries, including most of Europe and Australia.

The Biden administration has been pressured by the travel industry and Republican politicians to lift the mask mandate. Domestic airline executives have cited threats to the safety of airline employees, as they are essentially tasked with policing mask wearing.

The Transport Security Administration, which is responsible for airport security, indicated in March that government agencies are working with the CDC on “a revised policy framework” for when, and under what circumstances, masks should be required on forms of public transport.

Covid-19 cases are “starting to tick up a little bit,” particularly in areas including northern New England, New York, Colorado and Washington, DC, said David Dowdy, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health. Philadelphia on Monday became the first major US city to reimpose an indoor mask mandate.

Airlines have also called for an end to pre-departure testing requirements for international travel. Lifting them is expected to further increase demand for travel.