"We'll see what the situation is when we land. I do not need a photo op," Obama said en route to South Africa.
"The last thing I want to do is to be in any way obtrusive."
Meanwhile, the ANC has called on groups holding anti-US protests during Obama's visit to show restraint.
"It is our wish that the protests will themselves be carried out in a manner that reciprocally respects the rights of others who do not share the same view," the ANC said on Friday.
It welcomed Obama to South Africa and thanked him for his warm tribute to critically-ill former president Nelson Mandela.
"As we welcome President Obama and his family to South Africa, we also thank them for their kind words in Senegal that our beloved icon and statesman comrade Nelson Mandela … is a hero of the world.
"We thank them too for their prayers and thoughts as we thank all other peoples of the globe who continue to keep Madiba in their thoughts during this time."
Obama was due to land in South Africa later on Friday as part of a three-nation tour of Africa. A few hours before his arrival, protesters from various groups marched to the US embassy in Pretoria.
Some were Muslim activists protesting against US policies on the Middle East. ANC ally, the Cosatu, said it would protest during the visit about US foreign and trade policies.
The ANC call echoed statements by the presidency and Cabinet ministers to those who planned to protest during Obama's visit to do so peacefully.
The government's joint security operations team appealed to the public in Gauteng and the Western Cape not to gather on roadsides to sneak a glimpse of Obama and his convoy.
This request was made in the interest of public safety, said Brigadier Sally de Beer, spokesperson for the National Joint Operational and Intelligence Structure.
"It is requested that members of the public refrain from converging on those areas in the hope of catching a glimpse of the aircraft or vehicles in the security or transportation details, or even of the VIPs," she said in a statement.
"We have noticed during dry-runs that as soon as a helicopter hovered to prepare for landing, people were running across busy roads towards the aircraft.
"This not only places the pedestrians and road users at risk, it is very dangerous to approach a helicopter while its rotors are turning."
De Beer said all efforts were being made to ensure Obama's visit took place in a safe environment, and caused as little inconvenience as possible to the public.
"Those that do encounter minor inconveniences are requested to remain patient and to be co-operative with security forces and public safety officers.
"We remain committed to upholding South Africa's good reputation as host of secure international events and visits."
Obama is due to land in South Africa on Friday evening. He will hold talks with President Jacob Zuma on Saturday and visit Cape Town on Sunday. His visit formed part of a three-nation African tour which began in Senegal and would also take him to Tanzania. – Sapa