BUCHAREST, Romania — President Bush today said he remains committed to building a missile-defense system in Europe and will press outgoing Russian President Vladimir Putin to drop his objections to the project.

Bush said he was willing to cooperate with Putin on the plans and that he say as much to the Russian leader when the two meet this week. He says the system is needed to counter potential threats from the Mideast.

He also renewed urgent calls for NATO to start the admission process for Ukraine and Georgia despite a split among alliance members and fierce Russian objections.

The president said the two former Soviet states are ready for membership and that NATO leaders at a summit this week must make clear that membership will remain open to all European nations, no matter what Moscow thinks.

"We must make clear that NATO welcomes the aspirations of Georgia and Ukraine for membership in NATO and offers them a clear path forward toward that goal," Bush said in a speech ahead of a summit of alliance leaders in Bucharest.

"So my country's position is clear: NATO should welcome Georgia and Ukraine into the Membership Action Plan. And NATO membership must remain open to all of Europe's democracies that seek it, and are ready to share in the responsibilities of NATO membership."

He also called for NATO members to step up troop contributions in Afghanistan, citing Osama bin Laden's latest threats to Europe.

Bush says that if the alliance does press the offense in Afghanistan, Taliban and al-Qaida extremists will use the country to launch more attacks on the West.