The high-level meeting includes the leaders of the US, Russia, China, Japan and others
He spoke as leaders from the 21-nation Asia-Pacific Economic Co-operation (Apec) bloc met for roundtable talks.
Discussion is expected to centre on trade agreements and a regional anti-corruption initiative.
On Monday, the Japanese and Chinese leaders held talks for the first time on the sidelines of the summit.
Ties between the two Asian giants have been extremely tense
due to a territorial row over disputed islands in the East China Sea.
US deputy national security adviser Ben Rhodes said the US
welcomed the meeting as it was an opportunity to lower the simmering
tensions between the two countries.
Uncertain factors
On Tuesday, Mr Xi in his opening remarks pushed for a trade
liberalisation framework called the Free Trade Area of the Asia-Pacific
(FTAAP).
"Currently, the global economic recovery still faces many
unstable and uncertain factors," the Chinese leader said outside Beijing
where the summit is taking place.
The US and China are pushing separate wide-reaching trade agreements at the summit
"Facing the new situation, we should further promote regional
economic integration and create a pattern of opening up that is
conducive to long-term development."
China is proposing a two-year study on the FTAAP plan which will be presented to the Apec leaders for approval.
However, some say it could distract from another
wide-reaching trade agreement backed by the US called the Trans-Pacific
Partnership (TPP) which China is not part of.
Some Chinese commentators have said the TPP is a method to counter China's growing influence in the Asian region.
However, Mr Obama rejected this in an interview with China's
Xinhua state news agency, saying the US was in no way trying to contain
China.
Mr Obama pointed out that as major trade partners, the two countries were invested in each others futures.
"We want China and the Chinese people to succeed and
contribute to global security and prosperity, because it is good for all
of us," he said.
Apec, which includes the US, China, Japan, South Korea and Canada, accounts for more than 50% of global economic output.
In other developments:
- The US and China have agreed to grant visas valid for up to a
decade to visitors between the two countries, up from a maximum of one
year.
- Mr Obama, in the interview with Xinhua, said the US was willing
to strengthen counter-terrorism co-operation with China to stem the
flow of foreign terrorist fighters and crack down on terrorist funding
networks.
- China has pledged $10m (£6.3m) to support the Apec mechanism for capacity building.
- Australian leader Tony Abbot is expected to meet Russian leader
Vladimir Putin. Mr Abbot has pledged to hold a "robust conversation"
with Mr Putin over the downing of flight MH17 over Ukraine in July.