She said she was personally prepared to make the case for such a change.
Newly appointed French Prime Minister Edouard Philippe at the handover ceremony in Paris. In a move that will no doubt please Germany, Macron also announced the appointment of Édouard Philippe as his prime minister on Monday.
The German leader also said that she and Macron have an interest in moving forward with the establishment of a common asylum system within the EU and on the Defence Union.
"We share the common conviction that we can not only focus on Great Britain's departure from the European Union, but rather we have to discuss ways to deepen our cooperation among the remaining members of the European Union, among the members of the Eurozone", she said.
Briefing journalists before he travelled to Germany on his plans to "relaunch" the European Union, create a joint national budget, parliament, and finance minister for eurozone nations, Macron clearly caused concern amongst some.
Merkel said that, from Germany's viewpoint, treaty change would be possible, adding: "I would be ready to do this, but first we will work on what we want to reform".
"I will be an open, direct and constructive partner", Macron said.
A large group of onlookers, some carrying European flags, stood outside the chancellery as Mr Macron arrived. Euobserver reports in its article Macron and Merkel to "reconstruct" the European Union that two leaders have the "common conviction that [they] should not only deal with the United Kingdom exit" but that they should think of how to "deepen" and "strengthen" the European Union and the eurozone.
Speaking to BBC Radio 4's Today programme, Dr Ammon said: "We are happy to have a new star born in Europe, and that is Emmanuel Macron".
Meanwhile, Philippe said hours after his appointment on May 15 that he made a decision to accept the job Macron offered him because France is in a "unique situation".
Mr Philippe's age reinforced the generational shift in France's corridors of power and the image of youthful vigour that Mr Macron is cultivating.
There was a warm welcome for the new French president both from Angela Merkel and - unusually - a crowd singing and dancing outside the chancellory.
Mr Philippe is the mayor of the Normandy port of Le Havre, a trained lawyer and an author of political thrillers.
Paris: France's centrist President Emmanuel Macron named his government on Wednesday, appointing a mix of political hues to the top jobs as part of his promise to bridge the right-left divide.
The FN has only two outgoing lawmakers in the lower house of parliament, but polls show the party securing about 20 percent of the vote in the first round of the National Assembly election on June 11. The choice of Mr Philippe is aimed at drawing more defectors from The Republicans.
Emmanuel Macron's support for the Paris bid is seen as symbolically important, and his decision to meet Tuesday with the visiting International Olympic Committee delegation was one of his first moves since taking office Sunday.