(dpa) - Enlargement, Afghanistan and the issue of defence against internet-based attacks topped the agenda Thursday as NATO leaders gathered on the second day of a summit in Bucharest.
"Europe has to be united and secure. NATO's door has always been open, and that has not changed: the family will continue to enlarge," NATO Secretary General Jaap de Hoop Scheffer said as he opened formal talks between the leaders of NATO's 26 member states.
On Wednesday evening, NATO leaders agreed informally that they would formally invite Croatia and Albania into the alliance.
The invitation ceremony is set to take place at the end of the first working session on Thursday morning, in the presence of the two countries' top political leaders.
NATO's own leaders are also set to discuss updating their alliance's strategy to deal with new threats such as web-based cyber-attacks, assaults on energy infrastructure and missile strikes.
Cyber-defence has been a hot topic since pro-Russian hackers launched a massive campaign against Estonia's computer and information systems one year ago during a dispute over the relocation of a Soviet war memorial.
Energy security is also high on the global political agenda. Europe and North America both rely heavily on energy imports, making security of supply a pressing concern, and NATO states also fear that terrorists could target critical energy infrastructure.
However, NATO officials point out that both issues are primarily the responsibility of member states, and that Thursday's debate should focus on how the alliance can "add value" to matters.
Missile defence is the third highly-charged topic of the day. The United States is currently negotiating with Poland and the Czech Republic over plans to site elements of an anti-missile system on their soil - plans which have infuriated Russia and divided NATO.
On Thursday afternoon, NATO leaders are set to turn their attention to the ongoing UN-mandated mission in Afghanistan.
NATO leads the 47,000-strong International Security Assistance Force (ISAF) in Afghanistan. The force has scored military successes against the Taliban, but critics say that those successes have not been fully matched by reconstruction and stabilization projects.
NATO leaders are set to meet with the heads of organizations such as the Afghan government, European Union and World Bank to discuss how civilian and military bodies can best work together.