After Iran withdraws candidacy, matter could be forced to a vote on Friday.
Despite opposition from the West and the United States in particular, Syria appears determined to pursue its bid for a seat on the UN atomic watchdog's board, now that Iran is officially out of the running.But in a looming clash at the International Atomic Energy Agency's general conference here this week, Afghanistan - a US ally - also announced its candidature on Wednesday.
Diplomats said Kabul enjoys the support of a majority of the IAEA's 145 member countries.
The matter comes up for discussion on Friday and could be forced to a vote.
Members of the IAEA's 35-strong board of governors are designated and elected each year by the body's highest policy-making body, the General Conference.
Decisions are traditionally adopted by consensus, but if no consensus is possible, it goes to a vote.
A seat has become free for the so-called Middle East and South Asia (MESA) group with the expiry of Pakistan's one-year term.
Iran had also been seen as a potential candidate, but it pulled out in favour of its staunch regional ally Syria.
If MESA cannot agree on a single country, it will be up to the general conference to vote between the different candidates.
For the US and others, however, Syria would be unacceptable because of current allegations it was building a covert nuclear facility at a remote desert site called Al-Kibar until it was destroyed by Israeli bombs in September 2007.
Damascus has yet to clear up the allegations, which it has dismissed as "ridiculous".
Apart from allowing IAEA experts to inspect the suspect site in a one-off visit in June, Syria has not undertaken any further action to actively disprove the accusations.
"Having Syria on the board would be like having a suspected arsonist oversee the fire brigade," one conference participant told newswire AFP on condition of anonymity.
Syria, for its part, refuses to withdraw its candidacy, in spite of US-led opposition, saying it has the support of the Arab League.
But Afghanistan had the wider backing of other Islamic countries, a diplomat close to the IAEA said.
"In the OIC [Organisation of Islamic Conference], you can go through the list and you'll see the majority of people would vote for Afghanistan," the diplomat said.
"Albania is an Islamic country, so is Aberzaijan. There are countries in Africa that are Islamic and members of OIC that would certainly support Afghanistan, because we are an Islamic republic with a better, progressive constitution," the diplomat said.
The hope was that "by Friday, Syria will come to an understanding" and back down, the diplomat continued.
"It's simple maths. If 89 are for Afghanistan, out of a total 145, that's 56 countries there for Syria."
The diplomat said Afghanistan had approached numerous delegations and had already received great many letters of support from various capitals.
A conference participant, who also spoke on condition of anonymity, said Syria was running into a great deal of resistance.
"The Syrian ambassador is frantically canvassing IAEA members - and learning that he will lose," the participant said.
Kabul's permanent representative to the IAEA, Wahid Monawar, told AFP that he thought the time was right for Afghanistan to take a seat on the board.
"We believe that as a progressive nation, and a developing nation [we will] bring a better understanding of Islamic countries, the Islamic understanding, to the West and articulate the issues that need to be articulated," Monawar said.
"We believe this opportunity is right, the year is right. It's an opportunity for the Afghan people to benefit from the technology that is afforded by the agency."