French centrist Emmanuel Macron sought to establish his presidential credentials on Thursday by calling for international military intervention against Syrian President Bashar al-Assad if he is proved to have used chemical weapons.

The former economy minister is favorite to win France’s presidential election but faces criticism from his opponents that he is too inexperienced for the top job.

Macron, 39, interviewed for 2-1/2 hours on France 2 television, took a tough stance on the top foreign policy issue of the day, calling for military intervention against Assad if his government was found to have carried out a suspected chemical attack that killed at least 70 people on Tuesday.

“An international intervention is needed … My preference is that there should be an intervention under the auspices of the United Nations. A military intervention,” Macron said.

However, he said a military operation must be part of a “diplomatic and political roadmap.”

Russia has repeatedly used its veto in the past to protect the Syrian government from U.N. Security Council action.

Polls show Macron and far-right leader Marine Le Pen each winning about a quarter of the vote in the April 23 first round of the election, with Macron tipped to easily defeat Le Pen in the May 7 runoff.