Wall Street stocks finished a meandering session higher on Monday, shrugging off Moody's downgrade of US sovereign debt, which could balloon further.

All three major US indices finished with modest gains.

All told, the S&P 500 rose 5.22 points to 5,963, the Dow Jones Industrial Average added 137 points to 42,792 and the Nasdaq composite rose 4 points to 19,215.

The dollar retreated somewhat against the euro and other major currencies. But the move was less substantial than during most volatile stretches earlier this year.

In comparison with that turbulent period, a closely-watched volatility index remained relatively stable on Monday. Stocks have rallied since US President Donald Trump suspended many of his most onerous tariff measures.

Gold, seen as a safe haven investment, jumped more than one percent.

In Europe, London and Frankfurt erased early losses to close higher after UK and EU leaders reached a series of defence and trade accords at a landmark summit.

In company news, Walmart returned to the list of firms feeling a rollercoaster effect under Trump, after the US president slammed the retail giant for warning of price increases due to his tariffs.

Walmart shares finished slightly lower on Monday. (AFP)