The future of unsettled Manchester United midfielder Angel Di Maria was thrown into doubt here Saturday after it emerged the Argentine international had failed to join up with the club's US tour as scheduled.

Di Maria, who has been strongly linked to a move to French giants Paris Saint Germain, had been due to arrive in California on Saturday to join United's pre-season training camp.

But United manager Louis van Gaal told reporters after his side's 3-1 friendly victory over Barcelona at the Levi's Stadium that Di Maria had failed to board a flight to San Francisco.

"I have heard that he's not on the plane so I cannot say anything," van Gaal said.

"I have heard that he was not on the plane," he reiterated.

Di Maria had been excused from the first part of United's tour after playing in the Copa America along with fellow Red Devils team-mate Marcos Rojo.

Rojo had also failed to join up with the United squad, but van Gaal put the defender's no-show down to a passport issue.

"I heard Marcos Rojo was not on the plane, he had passport issues," van Gaal said.

"But Di Maria I do not know."

A report on the website of Britain's Daily Mail newspaper shortly before kick-off on Saturday said van Gaal had informed United's players that Di Maria was set to join PSG.

Di Maria joined United last year in a 59.7 million pound ($92.6 million) transfer from Real Madrid but has failed to settle during a difficult first season with the Premier League giants.