UN special envoy to Yemen Martin Griffiths is expected to discuss urgent humanitarian measures and resuming the political process with senior figures in the Iranian government on Sunday.
Mr Griffiths's first visit to Tehran is part of his efforts to support a negotiated solution to the five-year conflict in Yemen, which started when the Iran-backed Houthi rebels drove the government from the capital, Sanaa, in 2015.
A Saudi Arabia-led military coalition then intervened in an effort to restore the internationally recognised government.
“The special envoy’s immediate priority is to support agreement between the parties to the conflict on a nationwide ceasefire, urgent humanitarian measures and the resumption of the political process,” Mr Griffiths's office said.
As he began his two-day Iran trip, where he is due to meet Foreign Minister Javad Zarif, a meeting between the Gulf Co-operation Council and Egyptian officials was held in Cairo.
Egyptian Foreign Minister Sameh Shoukry welcomed GCC Secretary General Nayef Al Hajraf, who highlighted the importance of respecting the sovereignty of Arab states.
He was alluding to Iran, which GCC nations have long accused of meddling in neighbours' affairs.
Mr Al Hajraf also welcomed the US appointment of the new envoy to Yemen, Tim Lenderking, which comes after the Biden administration announced it would delist the Houthi militia as a foreign terrorist organisation.
Mr Griffiths has been shuttling around the region in recent years trying to build momentum for peace efforts and to find international agreement on how to end the conflict.
He has been trying to get the government and the rebels to resume political talks.
His visit follows remarks made by Yemen’s Prime Minister Maeen Saeed, who called for international pressure on Iran to move the Houthis towards peace, the state news agency said.
Mr Saeed told an EU delegation that the rebels were “implementing Iran’s agenda and are not concerned about the suffering of the Yemenis".
The delegation arrived in Aden, the interim capital of Yemen, on Saturday, in support of the unity government.
The officials included the ambassadors of Germany, Belgium, France, the Netherlands, Ireland, Finland, Sweden and the deputy ambassador of Norway to Yemen.
It is the first high-level delegation of diplomats in Aden since Yemen's unity government returned to the city in December.
Mr Saeed said the presence of the government “contributes to mitigating many of the existing repercussions".
“It will establish a new direction of relationships with Yemen's partners from donor countries and organisations, especially in the relief, humanitarian and development sectors,” he said.
Mr Lenderking was appointed the US envoy to Yemen last week.
A senior US diplomat and former deputy assistant secretary for Arabian Gulf Affairs, he is the first US envoy for Yemen since the war started in 2015.
The GCC welcomed the US's decision and said the move was "positive" for regional and international efforts aimed at ending the conflict.
Mr Al Hajraf stressed the importance of the US role in ending the Yemeni crisis, and its humanitarian and development assistance to the country.
"We are looking forward to working with Ambassador Lenderking," he said.
"His wisdom, capabilities and experience in the region will enhance the efforts of the international community towards finding a comprehensive solution to the Yemeni crisis and achieving security and stability in the region."
