ISTANBUL By getting Iran to agree to swap stocks of low enriched uranium that could have been used for making a nuclear bomb, Brazil and Turkey have thrust themselves into the unfamiliar centre of a global dispute.
They could have delivered a diplomatic coup with the deal struck in Tehran on Monday.
Or the deal could be dismissed by world powers as too little and too late for failing to address core concerns over Iran's nuclear programme.
Brazil's President Luiz Inacio Lula da Silva and Turkish Prime Minister Tayyip Erdogan have staked their international standing on Iran honouring the commitments it made to them.
Brazil and Turkey have rotating seats on the U.N. Security Council and covet a bigger role in the international arena. But critics say Lula and Erdogan could have overreached themselves over Iran.
"Turkey has taken a big risk because this can turn out to be very embarrassing," Faruk Logoglu, a former Turkish ambassador to Washington, said. "Iran is a very astute player in this game."
The United States sees Iran playing on uncertainties and divisions between the Western powers, Russia and China over sanctions. The sceptic in Washington might see the fuel deal as just another ploy, with Turkey and Brazil unwitting instruments.
Erdogan's desperation to break the stalemate between the West and Iran, and stop more U.N. sanctions being imposed on his country's neighbour is, however, understandable.
"The experience of Iraq is very fresh in the memory of Turkey," Logoglu said. "More than the prevention of sanctions, Turkey does not want to see another war in the region."
Turkey is rebounding strongly from recession, and Erdogan, a moderate Muslim leader, albeit with an Islamist past, is banking on the economic recovery helping him win a third term when the country votes next year.
Sanctions on Iran would hit Turkey hard. It has an $11-billion (7.6 billion pound) trade with neighbouring Iran and buys nearly 30 percent of its gas from the Islamic Republic.
Should it come to a vote, the only Muslim nation with NATO membership could risk Washington's ire by abstaining.
Erdogan and Foreign Minister Ahmet Davutoglu have risked irritating their U.S. ally by speaking out against sanctions.
"Davutoglu and Erdogan decided to carry out a high risk, high reward strategy towards Iran, and it has seemingly paid off," Sinan Ulgen, chairman of the Centre for Economics and Policy Studies in Istanbul, told Reuters.
Having seen the turmoil caused by the Iraq war, Turkey has pushed itself as a stabilising force in the region, mediating between Israel and Syria and the West and Iran.
Western facing in its foreign policy since the days of the Cold War, Turkey has sought to rebalance relations by strengthening ties with Russia and fellow Muslim states in the Middle East.
Condemnation of Israeli actions in Gaza, and readiness to risk past friendship with the Jewish state, has made Erdogan possibly the most popular leader among Muslims in the region.
Late last year, he dismissed talk of Iran having a nuclear weapons programme as mere "gossip," just one of several comments that made critics wonder whether NATO-member Turkey was in danger of slipping out of the Western camp.
But he won the confidence of the Iranian leadership and the agreement reached in Tehran demonstrated Turkey's clout.
"It shows the changing role of Turkey as a regional power with something to say on global issues," Soli Ozel, professor of international relations at Istanbul Bilgi University said.
Historic rivalry between Iran and Turkey would have made Tehran wary about giving Erdogan sole credit for any deal, but Lula's involvement removed those reservations.
As the leader of a far-off country, economically cushioned from the fall-out from the Iran crisis, and at the end of his presidency, Lula has far less at stake than Erdogan.
Lula's government is often criticized for timid foreign policy that avoids confrontation on issues such as human rights.
In 2009, he described the tumult over Iran's presidential vote as a routine electoral dispute, in contrast to broad criticism heaped on Tehran by international powers.
But brokering a deal with Iran could help Brazil show it has the diplomatic muscle as a leader of the developing world and help Lula carry out plans to become a global campaigner against poverty once he steps down as president this year.
But Lula also risks alienating himself from U.S. leadership that is already unhappy with his stance on Iran, and if this gambit fails he could be criticised as an unseasoned novice out of his depth.
(Additional reporting by Ibon Villelabeitia)