"The makeup of the Islamic Republic's negotiating delegation reflects this resolve and seriousness for taking serious steps towards the removal of the US' sanctions against the Iranian people," Ali Bagheri Kani told reporters.

"The issue of removal of the sanctions form the focus and principle priority of this round of the talks," he said, calling the bans "illegal and oppressive."

Earlier on Sunday, Bagheri Kani in an article published by the Financial Times slammed Western countries, especially the United States, for using talks as a tool to restrict Iran’s peaceful nuclear program.

“Western countries, in particular the US, work tirelessly to portray ‘negotiations’ as merely a process to restrict Iran’s legitimate and peaceful nuclear program, which is enshrined in international treaties and watched by oversight organizations,” Bagheri Kani said.

Bagheri Kani left Tehran for Vienna on Saturday to attend the seventh round of talks.

The US returned the sanctions in 2018 after leaving a historic nuclear agreement between Iran and others that had eliminated the coercive measures.

US President Joe Biden has alleged a willingness to re-enter Washington into the deal and lift the measures again. His administration has, however, not taken any meaningful steps towards the purpose, and even slapped new sanctions against the Islamic Republic.

Tehran has repeatedly lambasted Biden's team for keeping up the "maximum pressure" campaign of his predecessor Donald Trump.

Six rounds of talks have been held in Vienna to test the US self-proclaimed intention to lift the bans. The Austrian capital is to start hosting another round later in the day.

Earlier, Bagheri Kani held consultations with the Russian and Chinese delegations to the negotiations, which he hailed as "fruitful."

The diplomat has also sat down with Enrique Mora, deputy foreign policy chief of the European Union, which coordinated the talks that led to the conclusion of the nuclear agreement in 2015.