Pressure on Iran is intensifying, with key European countries and the United States moving ahead with plans to refer Tehran to the UN Security Council and Israel vowing not to let the Iranians develop nuclear weapons. But Russia and China - Iran's past backers - urged negotiations on Tuesday instead of confrontation, casting doubt on whether next month's International Atomic Energy Agency meeting will demonstrate a unified political will. Past opposition to such action by Russia and China led the Europeans and the United States to postpone referral. Russia and China have joined Europe and the US in criticizing Iran's resumption of uranium enrichment. But both would prefer to avoid Security Council involvement and are outright opposed to sanctions. The United States is the key backer of Security Council sanctions, but has thrown its weight behind the Europeans in hopes that time would work on its behalf in hardening anti-Iran sentiment.