BERLIN - German Chancellor Angela Merkel will use a planned visit to China this week to encourage Beijing to reduce its imports of Iranian oil, a German government source said on Tuesday.Last week, the European Union agreed to ban from July 1 all imports of oil from Iran, OPEC's second largest producer, in a drive to pressure Tehran into reining in its nuclear activities."It is in German interests that China does not raise its imports (from Iran). It would be good if China would reduce its imports," the government source told a news briefing ahead of Merkel's trip to China that begins on Wednesday.China has criticized the EU ban, saying it is "not a constructive approach."Beijing, the world's second largest crude consumer, has long opposed unilateral sanctions that target Iran's energy sector and has tried to reduce tensions that could threaten its oil supply.The 27-nation EU delayed until July the entry into force of the oil import ban because it also wants to avoid penalizing the ailing economies of Italy, Greece and others for whom Iran is a major oil supplier.The EU strategy will be reviewed in May to see whether it should go ahead.Western powers accuse Iran of planning to build nuclear weapons. Tehran says its nuclear program is for purely peaceful purposes.