USD fell against its major rivals in the European session on Tuesday, as investors' risk appetite improved after the World Health Organization (WHO) said that some treatments appear to be limiting the severity or length of the COVID-19 respiratory disease and said the organization is focusing on learning more about four or five of the most promising ones. "We do have potentially positive data coming out but we need to see more data to be 100% confident that we can say this treatment over that one," the WHO's spokeswoman Margaret Harris told reporters.

The U.S. Dollar Index (DXY), measuring the U.S. currency's value relative to a basket of foreign currencies, dropped 0.43% to 99.81.

However, the markets' sentiment remained clouded by the reports that major economies that eased coronavirus restrictions, including Germany and China, had seen increases in the number of positive Covid-19 cases. Market participants worried that a rebound in coronavirus infections around the world could embrace reopening activity.

The further decline of the U.S. currency was also limited by the latest comments of the Fed's representatives, which signaled that the policymakers were unlikely to take interest rates below zero to boost the economy, hit by COVID-19.