As one of the attendees, US President Barack Obama arrived in Lisbon, kicking off his talks with other NATO partners.

After wrapping up a 10-day swing through Asia, US President Barack Obama landed in Lisbon for a quick trip which might touch upon some sensitive issues.

He will face tough questions from NATO partners, such as his exit strategy in Afghanistan.

Barack Obama, US President, said, "And here in Lisbon I look forward to working with our NATO and our ISAF (International Security Assistance Force) partners as we move towards a new phase, a transition to Afghan responsibility that begins in 2011 with Afghan forces taking the lead for security across Afghanistan by 2014. So this summit is an important opportunity for us to align an approach to transition in Afghanistan."

NATO wants to sketch a roadmap that could pave the way for the alliance to wind down its involvement in the 9-year-old conflict in Afghanistan. The group is set to discuss the military alliance's future and agree on a new strategic concept.

They are also expected to extend a missile defense system and underline the importance of cooperation with strategic partners such as Russia.

Obama will also face questions about his handling of the domestic economy.

The US is still clinging to stimulus spending as a path toward recovery when many European nations are slashing spending and raising taxes. Many EU countries don't agree with the US's "quantitative easing" program.

Analysts say Obama must use his time with leaders to assure that his commitment to the trans-Atlantic alliance remains strong.