Brazil and Turkey on Wednesday urged their fellow UN Security Council members to heed a deal they struck with Iran over its nuclear program, in a last-minute bid to block a sanctions vote against Tehran.

"Brazil and Turkey are convinced that it is time to give a chance for negotiations and to avoid measures that are detrimental to a peaceful solution of this matter," the foreign ministers from the two countries said in a letter to the 15-seat world body.

The missive was sent as the UN Security Council was examining a US-drafted resolution calling for Iran to be punished with a new round of sanctions for pursuing uranium-enrichment activities.

The resolution was submitted to the vexation of Brazil and Turkey, which believed they had achieved a breakthrough on Monday when Iran agreed with them to deposit a significant part of its uranium stockpile in Turkey in exchange for better-enriched nuclear fuel.

Although the agreement was hailed as a diplomatic coup by Brazilian President Luiz Inacio Lula da Silva, the United States and its allies Britain and France said it did not go far enough to avert the sanctions push.

Washington fears Tehran is seeking to build a nuclear arsenal under cover of its civilian nuclear program -- a charge Tehran denies.

While Brazil itself admitted its three-way deal did not address the underlying issues boiling over, it said Iran's uranium-swap offer was a confidence-building measure that should be properly considered.

"This agreement is a new fact that has to be evaluated," Foreign Minister Celso Amorim, who led the Iran-Brazil-Turkey negotiations, insisted to reporters in Brasilia late Tuesday.

"To ignore this agreement would be to discard the possibility of a pacific solution," he said.

Lula, on a visit to Madrid Wednesday, said the UN Security Council should show "a willingness to negotiate."

The deal "is exactly what the United States wanted to do five months ago," he said.

A vote in favor of UN sanctions would be a blow to the efforts and prestige employed by Lula to secure the deal with Iran during a Sunday-Monday visit they made to Tehran.

Lula, who is stepping down as president at the end of this year, was hailed at home and in some big-name newspapers abroad as a master diplomat when the deal was announced.

But the United States, France and Britain poured cold water on the "triumph," saying Iran had broken many promises before and was defiantly saying it would continue to enrich part of its uranium stock staying in the country.

The United States, Britain, France, Russia and China -- the five veto-wielding permanent members on the UN Security Council -- have all indicated they support the idea of sanctions.

Brazil and Turkey are two of the 10 non-permanent members which have no veto. A resolution would require nine votes in the 15-seat council to pass.

Brazil's UN ambassador, Maria Luiza Ribeiro Vitto, spent just 40 minutes on Tuesday in a Security Council meeting discussing the issue before walking out and telling reporters her country "is not going to engage in the discussion right now."

In comments in Portuguese to Brazilian media that she refused to repeat in English to other journalists present, she said: "There is a new situation -- the deal -- and the time now is for diplomacy."

Brazilian newspapers reflected the government's rage.

"The US government is more than anything looking to show who runs a hierarchy of global power that emerging powers such as Brazil and Turkey see as outdated," the Folha de Sao Paulo newspaper opined.

It also claimed US President Barack Obama had exerted "exceptional" pressure to have Lula's visit to Tehran fail, quoting unidentified officials traveling with the Brazilian president, who was returning from Madrid on Wednesday.

The Estado de Sao Paulo newspaper said the UN sanctions push "will exacerbate the tensions between emerging countries without the bomb and nuclear powers."

It said Brazil, Turkey, Egypt and Indonesia feared the moves by the five permanent UN Security Council members held lessons for their own atomic ambitions.