The US president, George Bush, today told Iran it faced international isolation if it failed to curtail its nuclear programme, as the EU and US threatened further sanctions against Tehran.

The warning came in a declaration to be issued at the end of an EU-US summit in Slovenia today, a copy of which was obtained by theguardian.com.

The statement insisted Iran must "comply with international obligations concerning its nuclear activities," notably an end to uranium enrichment.

Washington and Brussels promised to "fully and effectively" implement existing UN security council resolutions on Iran's nuclear activities, warning also they were "ready to supplement those sanctions with additional measures".

Later, the EU's external relations commissioner, Benita Ferrero-Waldner, said these could include moves to freeze bank assets.

"We want to indeed show to Iranians that we mean it very seriously … [We are] particularly thinking of asset freezes of banks," she told reporters.

Bush, speaking at the summit at Brdo castle, the first stop on his last European tour as US president, said Tehran must transparently end uranium enrichment if it wanted closer ties.

"They can either face isolation, or they can have better relations with all of us," he said, adding: "Now's the time for all of us to work together to stop them."

Were Iran to end up with nuclear weapons, "the free world is going to say 'Why didn't we do something about it at the time?'" Bush said. "Now's the time for there to be strong diplomacy."

The US and others accuse Tehran of enriching uranium in order to produce nuclear weapons. Iran insists the programme is purely for civilian purposes.

Aside from Iran, the summit declaration – which outlined many general ambitions but very few specific policies – covered a range of subjects, including moves to tackle climate change, turbulent global financial markets and human rights abuses in Zimbabwe and China.

On global warming, Bush sounded a positive note, saying: "I think we can actually get an agreement on global climate change during my presidency." He warned, however, that no agreement on global warming could be effective without the cooperation of China and India.

On Zimbabwe, the summit declaration called on Robert Mugabe's regime to "cease the state-sponsored violence and intimidation against its people" ahead of a presidential run-off later this month.

It urged the UN secretary general, Ban Ki-moon, to immediately send a team to the country to "monitor human rights abuses and deter further abuses".

The leaders said they planned to maintain pressure on China over Tibet and human rights ahead of the Beijing Olympics, which opens in two months. They expressed their "deepest condolences" over the Sichuan earthquake, which killed an estimated 70,000 people.

The brief section on climate change reiterated standing commitments to UN targets on tackling global warming, notably the framework convention on climate change. However, there was an acknowledgement that any action would take place "in accordance with our respective policies", reflecting the different environmental concerns held by Washington and Brussels.

Little was expected of the summit, given that Bush now carries little weight as his last few months in office wind down. Last week, Bush's national security adviser, Stephen Hadley, warned the press not to get too excited ahead of the president's European trip, which will also take him to Germany, Italy, France, London and Belfast.

"I don't think you're going to see dramatic announcements on this trip," he said.

Emphasising the apparent indifference to Bush's presence, there were no demonstrations on streets near the summit venue in the Slovenian capital, Ljubljana.

Nonetheless, Bush's schedule is packed. He travels to Germany later today for talks with the German chancellor, Angela Merkel, before heading to Italy on Thursday. On Friday, he will meet Pope Benedict XVI in St John's Tower, a restored medieval structure in the Vatican gardens.

The pope usually greets world leaders in his study, but made the change in response to Bush's "cordiality" when Benedict was in the US in April, according to the Vatican.

The president will then go to Paris before ending his trip in the UK. He will meet the Queen and Gordon Brown before a brief stopover in Belfast.