During a general election that may see up to half of U.S. voters casting their ballots by mail, some states are warned by the U.S. Postal Service (USPS) that they need more time to count those ballots.

At least five states - Ohio, Pennsylvania, California, Missouri and Washington - have been told by the USPS that "major risk" voters do not have ample time to complete their ballots and return them on time under current state laws, according to Reuters' correspondence.

The Washington Post newspaper reported a total of 46 out of the 50 states and the District of Columbia have been alerted by the postal service.

The letters highlight the possibility that a meaningful number of mail votes in the November 3 presidential election might go uncounted if they are returned too late.

"State and local election officials must understand and take into account our operational standards and recommended timelines," USPS spokeswoman Martha Johnson said. She did not respond to questions about how many states in total got warning letters.

Election officials are bracing for a deluge of mail ballots as many states have made it easier to vote by mail to address concerns about public gatherings during the coronavirus pandemic.

Republican President Donald Trump said Thursday that he opposes additional funding to make mail voting easier.

Trump, who is trailing Democratic rival Joe Biden in opinion polls, has said without evidence that widespread mail voting could lead to fraud. However, public records show that he has requested mail ballots for himself and his wife Melania ahead of Florida's Tuesday primary election.

Election experts say mail voting is as secure as any other method. Biden and other Democrats say Trump is trying to interfere with the election, and former Democratic President Barack Obama said he was worried that Trump was trying to "kneecap" the postal service.

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The issue has taken on added urgency in recent weeks, as cost-cutting measures put in place by new Postmaster General Louis DeJoy have led to widespread mail delays.

Arizona Secretary of State Katie Hobbs, a Democrat, said on Friday that the changes could violate state laws against election tampering. She called for a criminal investigation.

SOURCE: Reuters news agency