Tension between the United States and Iran is intensifying despite signs, however weak it may be, of negotiations.

On Tuesday, the Iranian government said it had written to the US seeking an apology for alleging that Iran backed a plot to assassinate Saudi Arabia's ambassador to the US on American soil. Teheran's riposte was in response to a letter from Washington offering talks.

Last month, the US said that Manssor Arbabsayara, a 56-year-old US citizen holding both Iranian and US passports, and Gholam Shakuri, a member of Iran's Islamic Revolutionary Guard Corps, were charged with sponsoring and promoting terrorism, including plotting to assassinate the Saudi ambassador. Arbabsayara was arrested in the US, while Shakuri remains presumably in Iran.

The US quickly waged press and diplomacy "wars" against Iran to win the international community's support for its "cause", while Teheran fought back saying Washington's allegation was an "evil plot" aimed at isolating Iran.

We don't know which side is lying. But it is apparent that the US is sensationalizing the allegation with a motive. Washington's political intention behind the move is clear, too, considering the complicated situation in the Middle East.

The US and its Western allies got deeply involved in the political storm that began sweeping across countries in North Africa and the Middle East earlier this year. But Iran, an eyesore for the US, has emerged almost unscathed. Besides, the West thinks Iran used the precious opportunities to "develop its nuclear and missile programs", and make huge profits from rising oil prices during the Libya civil war.

Moreover, the political changes in the Middle East and North Africa, such as the stepping down of pro-US leader Hosni Mubarak in Egypt, will change the majority of Arabian countries' attitudes toward the US and Israel. Israel already seems to be isolated in the Middle East and even faces further confrontation from other countries in the region, which will eventually abate the US' influence in the region. And contrary to US politicians' expectations, Iran became the biggest winner of "Arab Spring".

No wonder, the US chose the "assassination plot" - a most suitable case - to demonize Iran. Given Iranian intelligence agencies' record of having formerly assassinated hostile individuals abroad, and that Adel al Jubeir, the Saudi Arabian ambassador to the US, is antagonistic to Iran, Washington thought it would be easy to gain support of American as well as international public if it portrayed Teheran as an Al-Qaida-like group that plots terrorist attacks on US soil.