However, the 64-year-old now appears very unlikely to see out the three-season contract that was supposed to be his crowning glory before retirement.
Saturday's 2-0 defeat at Stoke was the 20-time English titleholder's fifth Premier League game without a victory, coming after reverses against promoted teams Norwich and Bournemouth plus the loss at Wolfsburg that dumped United out of Europe's lucrative Champions League.
Van Gaal, a strict disciplinarian with unfaltering faith in his abilities, has cut an increasingly desperate figure in recent weeks.
After the Norwich game he admitted he was "worried" about his future, then walked out of his pre-Stoke press conference after less than five minutes, criticizing journalists for suggesting he was in danger of following Chelsea's Jose Mourinho in being sacked before 2015 was finished.
Saturday's performance did little to dispel such speculation. Stoke fans mocked Van Gaal -- one wearing a Mourinho mask carried a mock "P45" banner indicating that the former Barcelona and Bayern Munich coach would be fired in the morning.
"We didn't dare to play football in the first half and then we gave a very bad goal away. That was too much," Van Gaal said.
"They scored from a free-kick and then it was halftime. The second half was much better, we created one or two chances, and you have to score. The problem is we didn't dare to play. That is my analysis."
United's expensively-assembled squad did little to help their manager.
With out-of-form captain Wayne Rooney dropped to the substitutes' bench, Memphis Depay was given another chance to live up to his reported $27 million transfer fee -- but the young Dutch forward's mistake allowed Bojan Krkic to pounce for Stoke's 19th-minute opener.
The former Barcelona player was also involved in the home team's second goal seven minutes later; his free-kick was blocked by the defensive wall, but Marko Arnautovic blasted home a spectacular finish from outside the area.
The Austrian should have made it 3-0 before halftime, but was unable to find the target after beating the offside trap.
Van Gaal replaced Depay with Rooney at halftime, but United could not reduce the deficit. Marouane Fellaini had the best chance after being set up by Rooney, but was denied by Stoke keeper Jack Butland.
The result left United in sixth place after 18 games, having taken just two points out of the last available 15. It is the first time the team has lost four matches in a row since 1961.
Stoke ended the day just three points back in 11th place, on goal difference behind Everton and West Ham.
United next faces Chelsea, which later drew 2-2 with Watford in Dutch coach Guus Hiddink's first game of his second spell at the London club as interim manager.
Van Gaal admitted he has a big challenge in motivating his players to end the poor run of results.
"That is now the big issue. I have tried to do everything but the pressure shall be higher and higher with every match," he said after the Stoke game.
"That is the problem now. It is more difficult because I am also part of the four matches we have lost so people are looking at me and I have to deal with that, but more importantly the players have to deal with that because they are the ones who have to perform."
Van Gaal denied suggestions that he had given the wrong message during his pre-match conference on Tuesday.
"My message was that the media are saying and writing things that are not happening inside Manchester United. That was my message and not that I am hurt, because I am used to that," he said.
When asked about his future, he added: "I have said already in former press conferences that the club has to fire or sack me. Sometimes I do it by myself, but I am the one who wants to speak first with the board of Manchester United and with my members of staff or with my players, and not with you."
Leicester stayed top of the Premier League, despite losing its nine-match unbeaten run at Liverpool.
Belgium striker Christian Benteke, a first-half substitute, scored the only goal in the 63rd minute to inflict Leicester's first league defeat since September 26.
Arsenal was the victor on that occasion, but on Saturday Arsene Wenger's side remained second -- two points adrift -- after losing 4-0 at Southampton, with striker Shane Long scoring twice.
But the Saints were set on their way to victory by an early first half wonder goal from Cuco Martina, his strike from outside the penalty area reminiscent of a famous goal for Roberto Carlos for Brazil against France in 1997.
Martina's strike curved from outside the line of the post to leave Petr Cech with no chance of keeping it out.
It was Arsenal's first Boxing Day defeat since 1999, and 12th-placed Southampton's first win since November 7.
Third-placed Manchester City triumphed 4-1 against second-bottom Sunderland, while Tottenham stayed fourth with a 3-0 win over Norwich thanks to two goals from England striker Harry Kane -- and two assists from 19-year-old prodigy Dele Alli.
Spain striker Diego Costa scored twice for Chelsea at home to Watford, but after his second-half equalizer Oscar missed a penalty to leave the defending champion in 15th place -- two points above the relegation zone.