Jalili added that "hostile behaviors" directed toward Iran were detrimental to building confidence.
This was presumably a reference to the draconian sanctions imposed by Western governments against Tehran, which are crippling the Iranian economy. Oil exports have plummeted over the past several years, as has the value of Iran's currency.
"The purpose of any sanctions is to put pressure in order to get this process to work," said Ashton. "And I believe we should continue to work as hard as we possibly can to make sure we are successful and we reach a satisfactory resolution."
The so-called P5+1 governments are demanding that Iran come clean about its nuclear program, which they suspect includes covert development of nuclear weapons.
Iran consistently denies those charges, arguing it is enriching uranium and building nuclear reactors only for peaceful civilian energy needs.
Details of last February's offer from the six countries represented across the negotiating table from Iran have not yet been made public.
Last month, technical experts from Iran and the P5+1 countries met for more than 12 hours in Istanbul to discuss the proposal.
Iran's deputy chief negotiator said the Iranian proposal tabled Friday was based on a previous PowerPoint presentation that the Iranian delegation submitted during a round of talks in Moscow in June 2012.
"The Islamic Republic of Iran proposed a practical method to implement the Moscow plan in a smaller scale," Ali Baghery said in a statement issued to journalists Friday. The offer, he said, was aimed at establishing "a new bedrock of cooperation."
A call for 'concrete actions'
Washington has vowed it will continue to put pressure on Tehran.
"As long as Iran does not take concrete steps to address the concerns of the international community about its nuclear program, the dual-track process continues. And that pressure only will increase if Iran does not begin to take concrete steps and concrete actions," said a senior U.S. administration official in a telephone briefing to journalists this week. The official spoke on condition of anonymity.
Iran argues that as a signatory to the Nuclear Non-Proliferation Treaty, development of nuclear technology is an inalienable right.
On the eve of the two-day talks in Kazakhstan, Jalili repeated this position in a speech given at a university in Almaty.
"It is the right of the Iranian people to peaceful nuclear energy and most importantly to enrichment," Jalili said.
A report recently published by the Carnegie Endowment for International Peace concluded that sanctions are unlikely to force Tehran to give up its nuclear program.
The report, titled "Iran's Nuclear Odyssey," highlighted the fact that Tehran's quest for a nuclear program has been going on for more than half a century, beginning under the rule of the pro-American shah, Reza Pahlavi, and continuing under the revolutionary Islamic republic that overthrew him.
"The program's cost -- measured in lost foreign investment and oil revenue -- has been well over $100 billion," Carnegie said.