The head of the International Monetary Fund, Christine Lagarde, has warned that a US default could tip the world into recession.
American tracker funds were the preferred choice among Nucleus members in the third quarter, with the HSBC American Index emerging as the fastest growing fund on the platform.
US President Barack Obama will nominate Federal Reserve vice-chair Janet Yellen to be the next head of the US central bank on Wednesday, according to a White House official.
UK shares had a shaky start to the week as negotiations over the US debt ceiling continue to drag on.
Multi-asset managers are raising cash levels and adding to government bonds as fears over the US economy spook investors.
Christine Lagarde, managing director of the International Monetary Fund (IMF), has warned that the US' failure to raise its debt ceiling could be far worse than the country's current government shutdown.