US President Barack Obama on Monday met with German Chancellor Angela Merkel, French President Francois Hollande, British Prime Minister David Cameron and Italian Prime Minister Matteo Renzi during what is likely his last trip to Germany before leaving office in January.

Following the meeting, the Italian premier said Obama offered to support a NATO mission in the Mediterranean Sea near the Libyan coast.

Thousands of migrants have arrived in southern Italy since the beginning of the year, marking a sharp increase compared to the same period in 2015, according to the Italian interior ministry.

"Barack Obama said he was willing to commit NATO assets to block the traffic in human beings and the people smugglers that we refer to as modern slavers," Italian Prime Minster Matteo Renzi told reporters after the meeting, the Agence France-Presse news agency reported.

The White House confirmed Renzi's statement, saying that the leaders had urged NATO and the EU "to draw on their experience in the Aegean [Sea] to explore how they could work together to address in an orderly and humane way migrant flows in the central Mediterranen.

Europe's mission

However, Germany's Merkel said that any mission on the Mediterranean should be under an EU framework, instead of NATO.

"Through the NATO mission in the Aegean Sea, the US has shown its willingness to take part in combating illegal immigration here," Merkel said.

"The US is fully engaged and ready, in connection with the migration route from Libya to Italy, to share responsibility if necessary … However, we now have a European mission, EUNAVFOR, also called 'Sophia,' which is working quite well," the German chancellor added.

The leaders also discussed ways to bolster support for the new Libyan government as militant groups, including the self-styled "Islamic State" (IS), have made in-roads into the North African nation. Following the meeting, the US president boarded Air Force One and left Germany.

Merkel said "concrete proposals" for a NATO mission were not discussed

'Defining moment'

Obama's visit comes at a moment when Europe is struggling with several politically-charged affairs, including irregular migration to the bloc, a possible "Brexit" and terrorist attacks in European capitals.

"This is a defining moment, and what happens on this continent has consequences for people around the globe," the US president said, according to the Reuters news agency.

"If a unified, peaceful, liberal, pluralistic, free-market Europe begins to question the progress that's been made over the last several decades, then we can't expect the progress that is just now taking hold in many places around the world will continue," he added.