By Stefano Rebaudo and Rocky Swift (Reuters) -The U.S. dollar was mixed on Monday, coming off a six-day rally against the yen and a three-day losing streak versus the euro, as investors braced for a week packed with central bank meetings and trade negotiations. The U.S. Federal Reserve wraps up its two-day policy meeting on Wednesday, while rate decisions from the European Central Bank and the Bank of Japan are due on Thursday. U.S. President Donald Trump said the U.S. and China were set to "come away w ...