UN leader Ban Ki-moon will go to a summit of the Non-Aligned Movement in Tehran next week in the face of opposition by Israel and the United States, a spokesman said Wednesday.

Ban will "convey the clear concerns and expectations of the international community" on Iran's nuclear program, terrorism, human rights and the civil war in Syria, UN spokesman Martin Nesirky said.

Israel's Prime Minister Benjamin Netanyahu told Ban this month he would be making "a big mistake" if he attended the summit in Iran.

The US ambassador to the United Nations, Susan Rice, also advised Ban against going, diplomats said.

US State Department spokeswoman Victoria Nuland said this week it would be "strange" for Ban to attend the summit. "We, frankly, don't think that Iran is deserving of these high-level presences," Nuland added.

Iran is at the center of a showdown with the international community over its nuclear drive, has been accused of providing arms to Syria's President Bashar al-Assad and has also been condemned for inflammatory remarks by its leaders calling Israel a "cancerous tumor".

Ban's spokesman rebuffed the criticism, however.

Nesirky said the UN leader would "discuss frankly" the Syrian crisis but believed that Iran must be part of the solution, and that he would raise the other topics.

"By going he is making the extent of international concern all that much clearer," Nesirky told reporters.

Ban will be in Tehran from August 29 to August 31. He will have a private meeting with Iran's President Mahmoud Ahmadinejad, diplomats said. About 30 heads of state and government are to attend the summit on August 30-31.

The Non-Aligned Movement has 119 state members and the Palestinian Authority. Egypt's President Mohamed Morsi, Cuban leader Raul Castro and India's Prime Minister Manmohan Singh have all confirmed they will attend.

"It is a major international organization and Ban has no choice but to attend an event of this size and importance," said one UN diplomat.

"The concerns about Iran are shared by many of the leaders who will be at the summit, but it will not stop them going," added another envoy at the UN.

Tehran has outraged Israel with new comments by Ahmadinejad and supreme leader Ayatollah Ali Khamenei who repeated on Sunday that the "cancerous tumor" of Israel is the biggest problem confronting Muslim countries today.

Ban has slammed the Iranian statements and repeatedly stated that Iran, which is under UN sanctions over its nuclear program, must prove that its drive is peaceful. The United States and its European allies say that Iran is seeking a nuclear bomb. Tehran denies the charge.

A top UN official, under secretary general Jeffrey Feltman, said Wednesday that Iran appeared to be sending arms to Syria in violation of a UN Security Council sanctions resolution.

Ban "has repeatedly expressed his concern about the arms flows to the two parties in Syria which in some cases appear to violate resolution 1747", which prohibits Iran from making any arms exports, Feltman told a Security Council meeting.

The UN leader "takes seriously his responsibility and that of the United Nations to pursue diplomatic engagement with all of its member states in the interest of peacefully addressing vital matters of peace and security," the UN spokesman said.

In Iran, Ban "will use the opportunity to convey the clear concerns and expectations of the international community on the issues for which cooperation and progress are urgent for both regional stability and the welfare of the Iranian people. These include Iran's nuclear program, terrorism, human rights and the crisis in Syria," he added.