U.S. President George W. Bush, right, is welcomed by German Chancellor Angela Merkel upon his arrival at a government guest house in Meseberg, north of Berlin. Bush is on a two-day visit to Germany during his weeklong trip to Europe.

Kranj, Slovenia ? President Bush claimed progress Tuesday in his legacy-shaping drive to stop Iran from developing a nuclear bomb, winning European promises to tighten pressure on Tehran with U.N. sanctions and possibly other new penalties.

Bush, attending the final United States-European Union summit of his presidency, is working against time to secure one of the top foreign priorities of his presidency: halting Iran’s presumed ambition to join the global club of nuclear-armed nations and vastly increase its influence and reach.

“If they end up with a nuclear weapon, the free world is going to say, ‘Why didn’t we do something about it at the time, before they developed it?”‘ Bush said at the opening of a weeklong farewell tour of Europe.

“Now is the time for there to be strong diplomacy,” he said.

Oil-rich Iran has been barely pinched by the sanctions imposed so far by the United Nations and a solo U.S. effort to crimp Iran’s vast overseas financial operations. The U.S. penalties have had a ripple effect, though, with international banks scaling back their dealings with Iran.

Still, Iran has not only continued enriching uranium, producing material that could be used to power an electricity plant or make a nuclear bomb, but has expanded and improved its program

Since severing ties with Iran nearly three decades ago, Washington has had little leverage with Tehran. It needs cooperation from other nations that have meaningful economic ties to Tehran, a major energy supplier, to make any threats real.

Bush appeared to get closer to that goal in three hours of talks with leaders of the European Union, a political and economic coalition of 27 countries.

A joint declaration said the United States and Europe “are ready to supplement those (previous) sanctions with additional measures” if Iran does not halt enrichment. It also said they would “work together … to take steps to ensure Iranian banks cannot abuse the international banking system to support proliferation and terrorism.”

It was unclear whether this second pledge meant Europeans had signed on for the kind of harsh measures the U.S. favors, such as banning business with Iranian banks, or merely represented a repeat of previous calls for closer monitoring of dealings with them.

Stephen Hadley, Bush’s national security adviser, acknowledged that nations have been reluctant to implement the latest round of U.N. sanctions against Iran. He said officials are waiting to see what happens when the EU’s foreign policy chief, Javier Solana, visits Iran soon to present a package of penalities and incentives to entice its leaders into negotiations over the nuclear standoff. The offer, an update to one from 2006 than went nowhere, is being developed by the the United States, along with Britain, Germany, France, Russia, China, and possibly Italy.

Hadley said a rejection by Iran would open the door for the international community to “get much more aggressive” about enforcing the U.N. penalties. He said it also would allow nations to develop other steps together or act unilaterally to further squeeze Iran’s vast international business and banking relationships.

Bush continued to press his case later Tuesday, meeting with German Chancellor Angela Merkel at a government guesthouse near Berlin.