Iran opened an international conference against terrorism in Tehran on Saturday. The Supreme Leader of the Islamic Republic Ayatollah Ali Khamenei said in a message to the opening ceremony of the conference that fighting against terrorism is a responsibility for all countries. Terrorism is not a new phenomenon. However, the emergence of weapons of mass destruction has made it hundreds of times more dangerous, Khamenei said in his message. He said that Zionist regime of Israel has committed a number of terrorist acts against Palestinians and continues openly its terrorist acts outside and inside the Palestinians. The United States, Britain and some Western states, with a dark record of terrorist acts, have now added the claim of fighting terrorism to their rhetoric, said the Iranian leader. Taherian Mobarekeh, the secretary of the conference, said in the opening ceremony that the Islamic Republic is going to create global convergence and unity against terrorism by holding the conference in Tehran. Iranian Foreign Ministry spokesman Ramin Mehmanparast said Friday that the conference will confront the \"double standard\" of the world powers on terrorism. The world powers enter the scene under the pretext of campaign against terrorism when their interests are at stake but negotiate with terrorists for their own interests, Mehmanparast was quoted by the official IRNA news agency as saying. \"The measures which endanger lives of innocent people are condemned and they should be confronted ... It is necessary to forge consensus and ensure global unity to fight terrorism,\" he said. \"The conference is to form a platform where different views could be expressed. Participants from different corners and parts of the world can take part in the deliberation,\" Iran\'s Deputy Foreign Minister Mohammad-Mehdi Akhondzadeh told Press TV on Friday. The two-day International Conference of the Global Campaign against Terrorism has brought together senior officials from several countries. Tajik President Emomali Rahmon, Afghani President Hamid Karzai, Pakistani President Asif Ali Zardari and Iraqi President Jalal Talabani arrived in Tehran on Friday to attend the conference. Also, Sudanese President Omar al-Bashir arrived here on Saturday.