Deputy government spokesman Thomas Steg told a regular news conference that Berlin believed that neither country had the necessary political conditions to merit membership in the alliance.
"We are very reserved when it comes to the issue of deciding now on possible membership of Ukraine and Georgia," he said.
"This is solely linked to developments in each country and in the region. We expect the necessary resolution (of outstanding issues) and stabilization, pacification to succeed before this question can have a different response than is the case at the moment."
He said there were regional stability issues linked to Georgia's bid and called it an "open secret" that there was fierce debate in Ukraine about whether the country should join NATO.
"The situation in both these countries is decisive for the skepticism with which we view the question of membership," Steg said.
Chancellor Angela Merkel signalled early this month that she opposed Ukraine and Georgia joining NATO, saying the alliance should wait until the people of the two countries back membership and the region becomes more stable.
The two former Soviet states hope to win invitations to join NATO's so-called membership action plan, which helps aspiring countries prepare for future entry, when leaders gather at a summit in Romania beginning on Wednesday.
The issue has vexed Russia, with incoming president Dmitry Medvedev this week saying that the prospect of NATO coming closer to its borders was "extremely troublesome."
Despite strong support from the United States, plus Canada and most of the alliance's ex-communist members, there is reticence among many other states.
Countries such as Germany are wary of provoking a further row with Russia on top of a dispute over US plans to deploy an anti-missile system in the Czech Republic and Poland. They also point to a lack of public backing in Ukraine for the NATO policy
of the country's pro-Western leaders.
While Georgians are mostly in favour, concern there focuses on "conflicts" with the potential to create problems for the entire alliance if Tbilisi is given a green light. Separatists have controlled a swathe of northern Georgia since it broke free from the crumbling Soviet Union in the 1990s.