Renowned as a "soldier's soldier", Petain was promoted to commander-in-chief of the French armies in mid-1917, after victory at Verdun, rebuilding troop morale after a series of mutinies and other setbacks.
"I consider it entirely legitimate that we pay homage to the marshals who led our army to victory".
Touring battlefields ahead of a formal commemoration of the November 11, 1918, armistice that ended the war, Macron said Petain was worthy of the honor for his leading role in the World War I victory.
"He was a great soldier, it's a fact", Macron said, though he stressed that Petain had made "disastrous choices" during World War II. Jean-Luc Melenchon, head of the leftist France Insoumise (France Unbowed) party, called Petain "a traitor and an anti-Semite" whose "crimes and his betrayal can not be erased from history".
"The only thing we will remember about Petain is that he was convicted, in the name of the French people, of national indignity during his trial in 1945", he said in a statement.
The White House also confirmed that the Trump-Macron meeting would be the only bilateral meeting that Trump will hold during his France trip, ruling out the possibility of meeting with Russian President Vladimir Putin, who will also attend the commemorating event. Yet, that would change dramatically two decades later when Petain collaborated with Nazi Germany. His administration oversaw the deportation of over 76,000 French Jews to death camps on the Nazis behalf.
France's leading Jewish organization, known by the initials CRIF, issued a searing criticism of Macron's stance. "It judges the enormous and unworthy responsibility of a marshal who deliberately used his name and prestige as a cover for treason and the collaboration and deportation of thousands of Jews in France".
"I am shocked by this statement by Macron", CRIF president Francis Kalifat told The Associated Press. "Petain signed the [law on] the status of Jews that meant that Jews were excluded from public function, education and forced to wear the Jewish star".
Far-left leader Jean-Luc Melenchon said on Twitter that "Petain was a traitor and an anti-Semite. When one presides over France, one must measure up to its history".
The ceremony is another symbol of reconciliation between France and Germany, as Rethondes was also the site imposed by Nazi Germany on the French when accepting their surrender in 1940 during World War II, the Elysee said.
Later in the day, Macron, Merkel and UN General Secretary Antonio Gutteres will join other world leaders and representatives of civil society, for a peace forum held in the northeast of Paris.
After the war, Petain was sentenced to death for treason, though then-President General Charles de Gaulle, a longtime admirer of Petain's military feats of arms, reduced the punishment to life in prison.