The 31-year-old has 26 goals in 33 appearances for his country, who will kick off Russia 2018 in the opening match against the host nation in Group A.
Preparations for Juan Antonio Pizzi's side were dealt a blow by Tuesday's 4-0 defeat against Belgium but Turki Al-Sheikh, chairman of the General Sports Authority (GSA) of Saudi Arabia, tweeted on Wednesday to announce Al Nassr forward Al-Sahlawi would be operating in esteemed company for the next three weeks.
"It was agreed with Manchester United for Mohammed Al-Sahlawi to join for a training programme for three weeks," Al-Sheikh's post read. "May God benefit him."
Reports in Saudi Arabia maintain there is no intention on United's part to make an approach for Al-Sahlawi, who had been criticised for a "decline" in his performance in a Twitter post from Al-Sheikh reacting to the Belgium game.
Earlier this season, the administrator was present at the signing of a strategic partnership between United and GSA, under which the 20-time English champions will help the Saudi body to develop its football industry as part of its "2030 Vision" initiative.
—(@Turki_alalshikh) March 28, 2018
"This relationship is part of an exciting programme we are undertaking to transform sport in Saudi Arabia," he told the club's official website at the time of an agreement that will involve United lending business and sporting expertise to clubs and sporting authorities in the Gulf state.