The UN atomic watchdog does not rule out using its special inspections powers if Syria refuses to grant inspectors access to the remains of a suspected nuclear site, the head of the Vienna-based agency said on Tuesday. The comments by Yukiya Amano, director general of the International Atomic Energy Agency (IAEA), underlined growing frustration at Damascus continued stonewalling of the United Nations bodys investigation into the issue. On the Dair Alzour site, we havent had progress after I became director general (in late 2009), Amano told in an interview. We cannot wait forever, of course. For more than two years Syria has blocked IAEA follow-up access to the desert site that U.S. intelligence reports say was a nascent North Korean-designed nuclear reactor intended to produce bomb fuel.The site, known as either al-Kibar or Dair Alzour, was bombed to rubble by Israel in 2007. Syria, an ally of Iran, denies ever having an atom bomb programme. Amano said he had not yet received a response to a letter he wrote to Syrian Foreign Minister Walid al-Moualem on Nov. 18, the first time the IAEA chief has appealed to Syrian authorities directly, rather than just through his regular reports. In the letter, he asked the government to provide prompt IAEA access to relevant information and locations related to Dair Alzour and to cooperate with the agency in general. The United States has suggested that the IAEA may need to consider invoking its special inspection mechanism to give it authority to look anywhere necessary in Syria at short notice. Asked if he could consider this in the case of Syria, Amano said it was one of the tools at the agencys disposal. It is not ruled out. It is not decided to call for a special inspection either. The agency last resorted to special inspection powers in 1993 in North Korea, which still withheld access and later developed a nuclear bomb capacity in secret. The Wall Street Journal reported on Tuesday that the IAEA may soon issue a critical report on Syrias nuclear programme if it did not cooperate with the agencys investigation. Nothing has been decided. There are various ways to address this issue, Amano said.Syria has dismissed calls to grant U.N. nuclear inspectors prompt access to Dair Alzour, saying they should focus their investigation on Israel instead. Damascus has suggested the uranium traces came with Israeli munitions used in the attack. In a further sign of defiance, President Bashar al-Assad said in a Wall Street Journal interview this week Syria will not grant IAEA inspectors unrestricted access to possible nuclear sites because it would amount to a violation of sovereignty.