Washington, Sept. 15 -- The US Supreme Court has blocked President Donald Trump's plan to impose new restrictions on the distribution of mail-in ballots, dealing a setback to the administration ahead of this year's congressional midterm elections.

In an unsigned ruling, the court said the government is unlikely to succeed on the merits of its challenge to a lower court order blocking the proposed changes.

The ruling prevents the US Postal Service from implementing rules that could have allowed it to withhold mail ballots based on voter eligibility lists provided by states.

The administration had argued that the measures were needed to prevent fraud and ensure that ballots were sent only to eligible voters. Election officials and voting r...