Macron is visiting a migrant center before meeting security forces in Calais.
Negotiations over changes to the accords are in progress, including creation of a French-British team to handle cases of migrants with "legitimate" reasons to go to Britain, according to a top official in Macron's office who was not authorized to speak publicly. Macron used his speech to denounce the use of tear gas and physical violence against migrants, saying no breaches of professional ethics by police would be tolerated.
The migrant issue is set to become one of Macron's most tricky political tests because of splits in his newly formed Republic On The Move (LREM) party and public criticism from some of his closest allies.
One migrant applying for asylum in France, identified only as Ahmed, 25, said he travelled from Sudan through Libya and Italy to end up in Calais previous year, and told Macron he wants to "learn French, get training and find a job as auto mechanic".
Under Macron, France was "a country that is snatching blankets from migrants in Calais. Where people are getting lost, their hands and feet frozen, on the snowy slopes of the French-Italian border", the letter said.
He joined a chorus of criticism for the EU's "Dublin" rules which say asylum seekers must be dealt with in the country where they arrive, creating a huge burden for frontline states like Italy.
Macron has a strong negotiating position at the Sandhurst summit - he would prove a vital ally for May in this year's Brexit trade talks.
During a visit to the city during which he met residents and migrants seeking asylum, the French president delivered a speech focused on proposals to overhaul France's immigration and asylum policies to alleviate the pressure on the port city. "In no way will we let a "Jungle" spring up, or an illegal occupation of the territory".
Following the crackdown on the sprawling migrant camp dubbed "The Jungle" in October 2016, migrants in the region have struggled to find shelter and face routine raids by police if found sleeping rough.
But hundreds of people continue to camp out in Calais, hoping to stow away on trucks heading to Britain, a destination seen as an El Dorado by some migrants from Afghanistan and East Africa.
At stake with Britain is a 2003 agreement which effectively moved the United Kingdom border onto French territory, meaning the area around Calais has become a bottleneck for migrants hoping to cross to England. This was 50,000 fewer than the year before.
Under the agreement, illegal immigrants found in France can not enter Britain and are prevented from doing so by British border guards stationed in Calais.