Are relations between Syria and Iran cooling off? Has Tehran overdone things in Damascus? Huda al-Husseini, a veteran Lebanese correspondent, has information that seems to point in this direction. In a long and detailed article published last week in the Saudi-owned and London-based newspaper Asharq Al Awsat, she explains that not only were senior Syrian officials far from enthusiastic about Hezbollah's grandiose performance for Mahmoud Ahmadinejad when the Iranian president visited Lebanon last month, but Syria also appears to have been responsible for confiscating a large shipment of explosives that Iran was planning to send to Hezbollah via Italy.

According to the article, a container holding seven tons of RDX explosives was confiscated from the deck of the cargo ship Finland in an Italian port on September 22. The ship belongs to MSC Mediterranean Shipping Company, a Swiss shipping line, and was on its way from Iran to Syria. The explosives, which had been sent by Iran's Revolutionary Guards, can be used as ammunition for M-302 missiles, which have a 150-kilometer range, and M-600 missiles, which have a range of 250 kilometers and carry 500-kilogram warheads. The discovery of the explosives was published at the time in the Italian press.

What is unusual about this revelation, according to Iranian opposition sources who intercepted the Revolutionary Guards' report about the confiscation, is that it was a Syrian citizen who told the Italian authorities about the illegal cargo. According to an investigation carried out on the demand of Hezbollah and the Revolutionary Guards' representatives in Lebanon, employees of the Syrian Defense Ministry were the ones to inform on Iran. It appears that this investigation and its findings were the reason for the urgent visit to Syria at that time by Haidar Moussawi, the head of Iranian intelligence.

Feelings of suspicion and discomfort are apparently developing among Syria, Iran and Hezbollah, and the cargo in Italy is only one part of that trend. Tehran and Damascus were able to trust each other so long as it was clear that the other was not planning to encroach on its sphere of influence. Just as Syria does not intervene publicly or ostentatiously in Iraqi affairs - an area considered to be under Iranian influence - so Damascus expects Tehran to refrain from intervening too crudely in Lebanese affairs, at least not in a manner that portrays Lebanon as an Iranian protectorate rather than a Syrian one. But Ahmadinejad's visit to Lebanon, the presence of Revolutionary Guards there, and the transfer of explosive materials from Iran to Syria in a way that puts Damascus under scrutiny by the committee examining sanctions against Iran, raise questions about the quality of relations between the two countries.

The September incident apparently caused heavy damage to the Revolutionary Guards' efforts to send weapons and explosives from Iran to Syria, since it exposed Iranian sources in European countries and the methods Iran had been using to disguise and ship illegal cargo. One possibility is that, as the Italian authorities apparently suspect, Iran may have used close connections with the Italian mafia in the smuggling attempt. This is bolstered by the fact that it was Italy's anti-mafia unit that uncovered the cargo.

The authors of the Revolutionary Guards report consequently recommended that illegal cargo no longer be sent by sea but rather on land, via Turkey, among other countries.

According to the Iranian sources quoted in the article, a team of Iranian experts went to Syria to study firsthand the means of ensuring secrecy at the missile facilities meant for Hezbollah. The Syrians are investigating how the information was leaked.

Hezbollah as bargaining chip

Syria would like to leave Hezbollah as a bargaining chip in negotiations with Saudi Arabia over the international committee looking into the murder of Rafik Hariri, the former Lebanese president assassinated in 2005, or as a reward for Israel in case of a peace agreement. But Iran has other plans. It would like Lebanon to become an Iranian protectorate, through Hezbollah.

Both Iran and Syria do have a mutual interest in preserving stability in Lebanon. Tehran doesn't want a civil war, which it fears could cause Iran to lose its foothold in Lebanon, and Damascus is interested in ensuring Hezbollah does not cause a war with Israel that could also lead to an attack on Syria.

If the report about the Syrian agents who revealed the presence of the Iranian explosives is true, this does not necessarily mean that the two countries are about to break off ties - but it is a Syrian show of strength of a different kind than we have seen until now. This would not be the first time that Syria and Iran have not seen eye to eye with one another's policies. And as Syrian President Bashar Assad said a few months ago, the fact that the two countries cooperate on certain issues does not necessarily mean that they necessarily like each other.

Informing the authorities of a third country about the presence of explosive material has far-reaching implications. It indicates the extent to which Assad is prepared to tolerate the conduct of Syria, and Hezbollah. It is also a strong hint about what Assad is expecting from Iran and Hezbollah in anticipation of the indictment in the Hariri assassination affair. Hezbollah and Syria will not cooperate with the international tribunal hearing the Hariri case, but neither will Assad permit Lebanon to be shattered. The question now is whether Iran will act in line with its rational interests, or assume that it is sufficiently strong in Lebanon to twist Syria's arm.