WASHINGTON - More US states have announced plans to drop mask mandates amid still high baseline levels of new COVID-19 cases nationwide and increasing variant infections, drawing criticism from health experts.

Governors of Texas and Mississippi announced on Tuesday that they would halt mask mandates and reopen their states, allowing businesses to operate at full capacity.

Alabama Governor Kay Ivey announced Thursday she would lift her state's mask mandate in about a month. She said that beginning on April 9, wearing masks will be "a matter of personal responsibility and not a government mandate".

Earlier this month, governors of Iowa and Montana announced they would lift social distancing measures and mask mandates.

North Dakota issued a mask mandate in November 2020 which expired in January. Officials did not renew it due to a drop in cases and hospitalizations, while allowing for local safety protocols to be enacted.

These states joined more than a dozen other states that never required face coverings statewide.

The states' decisions to drop mask mandates came as the US Centers for Disease Control and Prevention (CDC) warned against complacency in the face of emerging coronavirus variants.

It drew great concern and criticism from officials and experts.

US President Joe Biden on Wednesday called it a "big mistake" for states to end mask mandates.

"Cases in the country are leveling off at rates just on the cusp of potential to resurge," CDC Director Rochelle Walensky said at a Wednesday briefing on the reopenings. She added the COVID-19 variant that first emerged in Britain, known as B.1.1.7, "looms ready to hijack our successes to date".

She stressed it is "critically important" that "individuals wear a mask, socially distance and do the right thing to protect their own health".

The decision of states leaders to roll back restriction measures is "inexplicable", said Anthony Fauci, the country's top infectious disease expert.

The baseline level of coronavirus cases needs to fall further before the country can confidently resume normal activities, even as the vaccine rollout accelerates, he said.

Fauci noted that in past periods of the pandemic, "when we started to pull back prematurely, we saw the rebound. We definitely don't want that to happen."

Currently nearly 2,600 infection cases of coronavirus variants have been reported in the United States, according to the latest data of the CDC.