The migrant crisis, security fears, and trade deal delays will dominate a summit of the EU's biggest nations and the US.
Monday's meeting of the G5 group of countries, which consists of America, Britain, Germany, France, and Italy, is expected to discuss deploying naval patrols in Libyan waters to try to halt the flow of migrants from war zones in Africa and the Middle East.
The two-hour gathering in Hanover, Germany, will also give Prime Minister David Cameron the chance to again emphasise the Remain camp's view that British influence is bolstered by its membership of the EU ahead of the June 23 Brexit vote.
German chancellor Angela Merkel said America and the EU needed to work together to deal with common threats.
"All of the security issues on the very doorstep of Europe can only be solved by joint trans-Atlantic efforts," Ms Merkel said.
US president Barack Obama will be at the summit, along with French president Francois Hollande and Italian prime minister Matteo Renzi will also be at the meeting, where the breakdown of the Syrian ceasefire will also be a major concern.
Security issues following the terrorist atrocities in Paris and Brussels were also likely to feature, along with moves to try to restore civil order to Libya after the chaos that has gripped the county since the British-French-American military intervention there to topple Muammar Gaddafi in 2011.
Mr Obama said he stood by the use of force, despite what was seen as recent criticism of Mr Cameron for becoming "distracted" after the fall of the dictator.
"I still believe it was the right thing for us to intervene. I do believe that it was important to plan and resource what would happen next. We didn't do it as effectively as we should have. The fact that we have a government of national accord obliges us to encourage it," Mr Obama said.
The massive Trans-Atlantic Trade and Investment Partnership (TTIP) deal that the US president is keen to see completed before he leaves office in January will also feature in the Hanover talks.
The host German city has been the site of major anti-TTIP demonstrations at the weekend as protesters fear the agreement would damage the environment and drive down labour standards.
Mr Obama stressed he would like to make serious progress on TTIP while he is still in the White House.
"I run my portion of the race and then I pass the baton to the next person.
"And my goal between now and the time I leave is to make sure that when I turn over the keys to my office that the desk is clean, and if the world is not completely tidy, that at least it is significantly better off," he said.