With less than 10 days before the deadline for a preliminary nuclear agreement with Iran, Tehran's supreme leader Ayatollah Ali Khamenei repeated a chanting crowd's call for "death to America" as he denounced U.S. "bullying" in the nuclear negotiation process.

"What the Iranian people don't want is imposition and bullying from America," he said during a speech on Saturday, reported Newsmax.

As the crowd began chanting "Death to America," Khamenei responded, "Of course yes, death to America, because America is the original source of this pressure," according to the Times of Israel.

"They insist on putting pressure on our dear people's economy," he said in reference to U.S.-led economic sanctions aimed at stopping Iran's nuclear program. "What is their goal? Their goal is to put the people against the system. The politics of America is to create insecurity."

Despite the cynical view held by the supreme leader, who has the final say on all matters of the state, Iranian President Hassan Rouhani and U.S. Secretary of State John Kerry both spoke Saturday of substantial progress in the negotiation process.

Rouhani said "achieving a deal is possible" by the March 31 target date for a framework agreement, according to The Associated Press.

Kerry remained more cautious in his assessment, telling reporters after six days of negotiations in Switzerland that the talks made "substantial progress" but "important gaps remain," according to AP. Kerry called for Iran to make "fundamental decisions" that prove to the world it has no interest in pursuing nuclear weapons.

"We have an opportunity to get this right," Kerry said.

Iran has long insisted its nuclear program is for peaceful and civilian purposes only, like nuclear energy and medical technology, while the West believes that Iran is pursuing the development of nuclear weapons, and has imposed economic sanctions to deter such pursuits. As part of the nuclear deal, the West has offered to ease some of those sanctions, which have significantly impacted the well-being of the Iranian people, in exchange for verifiable evidence that the country is not pursuing nuclear weapons. A final agreement deadline has been set for the end of June.

In a video message to the Iranian people celebrating the Persian new year, President Barack Obama said, "Together with the international community, the United States has said that Iran should have access to peaceful nuclear energy, consistent with Iran's international obligations." 

"So there is a way for Iran - if it is willing to take meaningful, verifiable steps - to assure the world that its nuclear program is, in fact, for peaceful purposes only," Obama continued.

Khamenei spoke of such accusations on Saturday, saying, "They raise the issue of an atomic bomb. They know themselves that we are not pursuing nuclear weapons. But they just use that as an excuse to pressure the Iranian people."

In Obama's video, he suggested that successful nuclear negotiations could build trust and lead to the development of other "possibilities that can bloom."

But Khamenei responded by denouncing Obama's suggestion. "Negotiations with America are solely on the nuclear issue and nothing else," he told the crowd on Saturday, according to AP.

"We do not talk with US over regional issues. In the regional issues, America's goals are completely opposed to our goals."

Both the U.S. and Iran are fighting against the Islamic State group in Iraq, and while the two countries are not coordinating operations together, reports indicate that the Iraqi government has asked Iran to conduct air strikes against the Islamic State in Iraq.