President Hassan Rouhani has pledged that Iran will abide by its commitments in the nuclear agreement reached in Switzerland yesterday.
He said Iranians will "remain loyal and stand by the promises" they made and that they "do not seek to deceive" the international community.
The president addressed the nation today, a day after Iran and six world powers announced after talks in Lausanne that they had reached a set of understandings on how to curb the Iranian nuclear programme. They face a June 30 deadline for a final deal.
Mr Rouhani also called on the world powers to fulfil their part of the deal, a reference to the further lifting of sanctions imposed on Tehran over the controversial programme.
Earlier, Iran's hard-liners criticised the tentative agreement, saying the deal is a bargain for the West and a disaster for Iran.
And supporters of the deal compared Iran's conservative opposition to the Israeli government - which remains heavily critical of the agreement.
Hossein Shariatmadari, an adviser to Iran's Supreme Leader Ayatollah Ali Khamenei and editor of the hard-line Kayhan daily, told the semi-official Fars news agency today that Iran exchanged its "ready-to-race horse with a broken bridle".
Another conservative analyst, Mahdi Mohammad, referred to the Fordo underground uranium enrichment facility, telling the news outlet that under the deal "a disaster happened in Fordo".
As part of the deal, Iran agreed to stop enrichment at Fordo, changing the facility to a nuclear research centre. The preliminary agreement places various limits on Iran's nuclear programme in exchange for an end to crippling economic sanctions.
Iran's Foreign Minister, Mohammad Javad Zarif, who signed the agreement, received a hero's welcome on his return to Tehran today from the latest round of talks.
Crowds of cheering supporters surrounded his vehicle and chanted slogans supporting him and President Rouhani.
One of the chants also offered sarcastic "condolences" to both Israel and to the Kayhan newspaper - which has opposed the negotiations from the start.
Mr Zarif tried to reassure Iranians that the country's nuclear programme will continue but said any negotiation requires give and take.
"It is not supposed to be one party receiving all the concessions and the other party surrendering," he said.
He also expressed his gratitude for Ayatollah Khamenei's support for his team and said yesterday's agreement will be a "base for drafting the final agreement" in July.
Another member of the negotiating team - Ali Akbar Salehi, the head of Iran's atomic agency - said: "I see the future very bright and shining."
The criticism from conservatives is part of a pattern of longstanding opposition by hard-liners against the policies of moderate President Hassan Rouhani, who has promised improved relations with the outside world.
Earlier yesterday, Ahmad Tavakkoli, a prominent conservative politician, wrote a letter to Mr Rouhani saying the agreement needs ratification by the country's conservative-dominated parliament.
But supporters of the negotiations have claimed that the nuclear talks have been conducted under the direct supervision of Ayatollah Khamenei, and therefore do not require parliamentary approval.
Ayatollah Khamenei, who has the final say on all state matters, has not made any public comment on the deal.
Iran and the global powers sealed a breakthrough agreement yesterday outlining limits on Iran's nuclear programme designed to prevent the country from developing atomic weapons.
The West has long suspected Iran is pursuing a nuclear weapons programme. Iran denies the charge, saying its nuclear research is focused on peaceful purposes like power generation and cancer treatment.