Iran's Chief Nuclear Negotiator, Saeed Jalili, has warned major western powers to stop threatening Iran over its nuclear programme. <br/><br/>Speaking in Beijing, following talks with senior Chinese leaders, he said Beijing had agreed that sanctions against Teheran would be ineffective. But, he refused to say whether China would support tougher measures. <br/><br/>Earlier, the US President Barack Obama discussed the Iranian nuclear issue in an hour-long telephone call with China's President Hu Jintao.<br/><br/>A US White House statement said, Mr. Obama underscored the importance of working together to ensure that Iran lives up to its international obligations. The two leaders also discussed the importance of implementing G20 agreements to boost economic growth.<br/><br/>The US and China have disagreed recently over Tibet, trade and Taiwan. China was upset when US President Barack Obama met Tibet's spiritual leader, the Dalai Lama. It was also angered by Taiwan securing a weapons deal from the US. <br/><br/>The US has supported the internet search company Google in its concerns over censorship in China, and other trade rows persist. One issue where China and US are in agreement is the need to bring North Korea back to the negotiating table over plans to end its nuclear programmes.