French President Francois Hollande has vowed to dismantle the "Jungle" migrant camp "definitively, entirely and rapidly" by the end of the year, during a visit to the port of Calais.
He strongly urged the UK to "play its part" in the humanitarian effort.
Mr Hollande was meeting police, port officials, and politicians but is not expected to visit the camp itself.
The fate of the camp and up to 10,000 people living there has become central to France's presidential campaign.
Mr Hollande said that just because the UK had made a "sovereign decision" - an apparent reference to the UK's vote to leave the European Union - it was not "absolved from its obligations to France".
He said he was determined that the UK government would support the humanitarian effort, and said his own government was committed "until the end".
Between 7,000 and 10,000 migrants and refugees live in the Jungle amid squalid conditions, many of them hoping to enter the UK illegally by hiding on lorries crossing the English Channel.
Mr Hollande paid tribute to the efforts of local security forces, and said he had "a clear message for the traffickers: you won't be trafficking any more".
A UK-funded wall 1km (0.6 miles) long is being built along the main road to the port in an attempt to deter would-be stowaways. The UK government has not confirmed the cost, but it is reported to have contributed about £1.9m (€2.2m).
Work began last week, and is due to be finished by the end of the year.
What is the 'Jungle'?
- The "Jungle" camp is near the port of Calais, and close to the 31-mile Channel Tunnel
- Officially, about 7,000 migrants live in the camp - humanitarian groups say the number is closer to 10,000
- Despite an increasing population, the camp's size was halved earlier this year
- But the camp's population has continued to rise, and reports of violence have increased
- Many migrants attempt to hide themselves in cargo vehicles entering the Channel Tunnel
- The area has been hit by protests from both locals and truck operators
Half the Jungle camp was dismantled earlier this year and it has become a major issue ahead of France's presidential elections, which take place next spring.
Ex-President Nicolas Sarkozy, who is among seven candidates seeking the Republican nomination, visited Calais last week.
As interior minister, Mr Sarkozy signed the 2003 Le Touquet treaty, which allows British immigration officials to check passports in Calais. Without it, UK officials would have to wait until people and vehicles arrived on British soil.
However, during a speech in Le Touquet last week, Mr Sarkozy said: "Those who are here in Calais and who want to cross to England should be processed in England by the English."
Speaking on Saturday, Mr Hollande promised to set up "reception and orientation centres" to take in asylum seekers. A dignified welcome would be given to people who filed for the right to asylum but anyone who was unsuccessful would be deported, he said.
France's Socialist president has not yet announced whether he will run for a second term.