US President George W. Bush renewed urgent calls Wednesday for NATO nations to allow Ukraine and Georgia to start the admission process, over Russian objections, and to counter Osama bin Laden's latest threats to Europe by stepping up their efforts in Afghanistan. On the eve of his last NATO summit, Bush lobbied fellow leaders for NATO expansion. He said the alliance should be open to all European democracies - for now the former Soviet republics of Ukraine and Georgia but also others in the future. "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," the president said. "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 added. Bush also called for NATO members to boost troop contributions to Afghanistan, where there are fears that Taliban and al-Qaida extremists are resurging. He noted that bin Laden in a recent audiotape had renewed threats to strike in Europe.