Ahead of what is now certain to be a contentious meeting with President Bush today, President Chirac of France reneged on his previous support for a united international approach to halting Iran's nuclear program. In two interviews on the eve of his trip to Turtle Bay to attend the U.N. General Assembly, Mr. Chirac threatened to restart negotiations with Iran. His comments called into question the united position of the five permanent members of the Security Council and Germany, whose foreign ministers had said that unless Iran suspended enrichment by the end of August, the council would consider punitive measures....