Iranian supreme leader Ali Khamenei banned on Monday holding any form of direct talks with the United States, rejecting an offer by President Donald Trump for unconditional dialogue. "I ban holding any talks with America ... America never remains loyal to its promises in talks ... just gives empty words ... and never retreats from its goals for talks," Khamenei was quoted as saying by state television. On July 30, Trump said he would be willing to meet Iranian President Hassan Rouhani without preconditions to discuss how to improve ties after he pulled the US out of the 2015 Iran nuclear deal, saying: “If they want to meet, we’ll meet.” Earlier, Khamenei said that internal mismanagement, not just US pressure, was to blame for his country’s economic crisis. “I do not call it betrayal but a huge mistake in management,” he added in a speech in Tehran, according to tweets released on his official account. "Economic experts and many officials believe the cause of this issue is not foreign, its internal," he continued. "Not that sanctions dont have an impact, but the main factor is how we handle them." He said that internal management needed to improve to help the country better weather newly re-imposed US sanctions. He referred specifically to the collapse in the currency, which has lost around half its value since April. "If our performance is better, more prudent, timely and effective, sanctions will not have that much effect and can be resisted," he added. Washington re-imposed strict sanctions against Iran last Tuesday and Trump has threatened to penalize firms from other countries that continue to operate in Iran. The sanctions prevent Iran from trading in gold and precious metals. They also ban purchases of US dollars by Iran and sanction its automotive sector. Unless Iran’s clerical rulers comply with the US demands, more sanctions targeting Iran’s oil and shipping industries are set for November. There have been widespread protests and strikes in Iran in recent weeks over high prices, unemployment and the wider management of the economy. Analysts say US hostility, including its withdrawal from the nuclear deal and re-imposition of sanctions, helped fuel the run on Irans rial. But many say it has only exacerbated long-standing problems within Iran -- and pressure has mounted from within the system on Rouhani to improve his management of the economy and tackle corruption. Iranian officials have blamed “enemies” for the fall of the currency and a rapid rise in the price of gold coins, and more than 60 people, including several officials, have been arrested on charges that carry the death penalty. “The fall of the rial and the increase in gold coin prices are major economic problems... The corrupt people (officials) should be punished firmly,” Khamenei said told a gathering attended by thousands of Iranians, state TV reported. Khamenei on Saturday called for “swift and just” legal action by new courts set up to tackle corruption after the head of the judiciary said Iran was facing an “economic war”, Iranian media reported.