President Donald Trump has said that his campaign will join an improbable case before the US Supreme Court challenging election results in Pennsylvania and other states.

Mr Trump’s latest move comes after the Supreme Court rejected a last-gasp bid to reverse Pennsylvania’s certification of US President-elect Joe Biden’s victory in the state.

The court has asked for responses by Thursday.

Out of the roughly 50 lawsuits filed around the country contesting the November 3 vote, Mr Trump has lost more than 35 and the others are pending, according to an Associated Press tally.

The suit from the Texas attorney general, Republican Ken Paxton, demands that the 62 total Electoral College votes in Georgia, Michigan, Pennsylvania and Wisconsin be invalidated. That is enough, if set aside, to swing the election to Mr Trump.

Mr Paxton’s suit repeats a litany of false, disproven and unsupported allegations about postal votes and voting in the four battleground states.

Mr Trump said: “We will be intervening in the Texas (plus many other states) case. This is the big one. Our Country needs a victory.”

Legal experts dismissed Mr Paxton’s filing as the latest and perhaps longest legal shot since election day, and officials in the four states have sharply criticised Mr Paxton.

The Supreme Court refused to call into question the certification process in Pennsylvania. Governor Tom Wolf has already certified Mr Biden’s victory and the state’s 20 electors are to meet on December 14 to cast their votes for the former vice president.

Mr Biden won 306 electoral votes, so even if Pennsylvania’s results had been in doubt, he still would have more than the 270 electoral votes needed to become president.

Shortly before tweeting about joining Mr Paxton’s case, Mr Trump distanced himself from the Pennsylvania challenge, saying it was not his.

He said: “The case everyone has been waiting for is the State’s case with Texas and numerous others joining.”

The court’s decision not to intervene in Pennsylvania came in a suit led by Republican congressman Mike Kelly and congressional candidate Sean Parnell, who lost to Democrat representative Conor Lamb.

“Even Trump appointees & Republicans saw this for what it was: a charade,” Mr Lamb said on Twitter.

In court filings, lawyers for Pennsylvania and Mr Wolf, said the suit’s claims were “fundamentally frivolous” and its request “one of the most dramatic, disruptive invocations of judicial power in the history of the Republic”.

“No court has ever issued an order nullifying a governor’s certification of presidential election results,” they wrote.

Having lost the request for the court to intervene immediately, Greg Teufel, a lawyer for Mr Kelly and Mr Parnell, said he would request that the court consider the case on its underlying merits on an expedited basis.

Still, hopes for immediate intervention concerning the election “substantially dimmed” with the court’s action on Tuesday, Mr Teufel said.

In their underlying suit, Mr Kelly, Mr Parnell and the other Republican plaintiffs had sought to either throw out the 2.5 million postal votes submitted under the law or to wipe out the election results and direct the state’s Republican-controlled legislature to pick Pennsylvania’s presidential electors.

The Republicans argued that Pennsylvania’s expansive vote-by-mail law is unconstitutional because it required a constitutional amendment to authorise its provisions. Just one Republican state lawmaker voted against its passage last year in the Republican-controlled legislature.

Mr Biden beat Mr Trump by more than 80,000 votes in Pennsylvania, a state Mr Trump had won in 2016. Most postal votes were submitted by Democrats.