Zhejiang: US President Barack Obama arrived in China on Saturday for his final visit as president, intent on cementing the "pivot" to Asia undertaken during his administration.
Obama was welcomed by an honour guard as Air Force One landed in the eastern city of Hangzhou, which is hosting the G20 summit of global economic powers.
But there was also tension on the tarmac, with angry words exchanged when a Chinese official remonstrated with National Security Advisor Susan Rice about where she could stand.
Hangzhou is under ultra-tight security, with a quarter of its residents encouraged to leave and potential troublemakers detained as the ruling Communist Party takes every measure to prevent any possible wrinkles.
Later on Saturday, Obama will hold private talks with Chinese President Xi Jinping at the city`s picturesque West Lake, dotted with islands and a favoured subject for Chinese artists.
The meeting is expected to focus on the fight against global warming, after China on Saturday ratified the Paris climate accord and with the US tipped to follow suit, taking the pact a giant step forward.
Tackling climate change has become a bright spot in often difficult relations between the two powers.
But Xi and Obama will also discuss tensions in the South China Sea, where Beijing`s territorial claims, and its construction of artificial islands in disputed waters, have set the region on edge.
On Sunday, Obama is to hold talks with Theresa May for the first time since she became British prime minister in the wake of the landmark vote to leave the European Union.
Syria will shift into focus when Obama meets his Turkish counterpart Recep Tayyip Erdogan on the sidelines of the summit.
Relations between Washington and Ankara have soured following an attempted coup against Erdogan and Kurdish advances along Turkey`s southern border.
Erdogan has accused the United States of harbouring a Turkish cleric he accuses of plotting the coup.
US officials insist they will extradite Fethullah Gulen if Turkey can present proof he was actually involved.
The spat has soured public perceptions of the United States in Turkey and risks undermining a deep security relationship between the NATO allies.
Tensions have been further strained by Turkey`s bombing of Kurdish positions in northern Syria.
The targets included Kurdish groups that are backed by Washington and seen as integral to the fight against the Islamic State group.
Ankara accuses them of being in league with the Kurdistan Workers Party (PKK), a group which has claimed responsibility for deadly attacks inside Turkey.
Obama could also take the opportunity to meet with Russian President Vladimir Putin, as their foreign ministers work to reach a deal that would ease fighting around Aleppo.
After the G20 talks conclude Monday, Obama will travel to Laos which is hosting the Association of Southeast Asian Nations (ASEAN) summit.