Beijing (CNN) -- The Sudanese president was scheduled to arrive in China on Monday, but the visit has been delayed without official explanation, Chinese ministry officials said.
Omar al-Bashir is the subject of an International Criminal Court arrest warrant for genocide, war crimes and crimes against humanity in the region of Darfur, where war has continued since 2003.
The Chinese Foreign Ministry said it had no information about why al-Bashir's arrival has been delayed. The Sudanese Embassy in Beijing said it did not know how the delay would affect his schedule.
Al-Bashir left Tehran, Iran on Sunday to attend a conference on combating terrorism, the state-run news agency in Sudan reported.
His plane left Iran to go to China but returned to Iran because of concerns over attempts to enforce the international court's warrant, senior government officials in Sudan said.
There were fears that countries that recognize the International Criminal Court would take action if al-Bashir's plane crossed their airspace on its way from Iran to China, the officials said.
China voted against the statute that created the International Criminal Court and is not among more than 100 countries that recognize it.
Prior to his trip, the Sudanese leader gave an interview with China's state-run news agency, Xinhua, in which he touted the longstanding ties between the two nations.
"We regard China as the strategic partner for Sudan in various fields, including the political, economic, commercial and cultural," al-Bashir said in the interview, published Sunday by Xinhua. "China does not interfere in the internal affairs of others. The success of the Sino-Sudanese cooperation has pushed the African countries to search for the real and loyal partner."
Last week, the advocacy group Human Rights Watch called China's invitation to al-Bashir "an affront to victims of heinous crimes committed in Darfur."
"Al-Bashir's flouting of international arrest warrants should be cause for condemnation, not for an invitation," said Richard Dicker, the group's international justice director. "Beijing should instead be using its influence to press for justice in Darfur."
The Sudanese president has deflected opposition to him, telling Xinhua in a story posted Saturday that Western nations went after him and his forces in order to "cover up the acts committed in Iraq and Afghanistan."
Al-Bashir, who became Sudan's president in 1993, is scheduled to be in China through Thursday at the invitation of its president Hu Jintao, according to Xinhua.
This will be his fourth visit to the Asian nation, after trips there in 1990, 1995 and 2006, when he attended a Sino-Africa Cooperation Forum summit in Beijing.
CNN's Nima Elbagir contributed to this report