A U.S. sovereign downgrade by Moody's has exacerbated investor worries about a looming debt time-bomb that could spur bond market vigilantes who want to see more fiscal restraint from Washington. The ratings agency cut America's pristine sovereign credit rating by one notch on Friday,

Long-dated Treasuries fell on Monday as investor attention turned to the US ballooning debt after Moody’s Ratings stripped the nation of its last top credit rating.

Investors will get the first chance to react to Moody’s downgrade of the U.S. credit rating late Friday over rising government debt and they’ll also look for more progress from President Trump on trade deals as the week kicks off.

China on Monday called on the United States to take responsible policy measures to maintain the stability of the international financial and economic system and safeguard the interests of investors.

Investors faced yet another bumpy start to the trading week with US assets coming under fresh pressure, although it’s mounting concern over American debt rather than tariffs generating the volatility this time.

Rising deficits, reduced foreign demand, and investor unease over trade policy drive bond market turbulence and broader risk aversion.

Here are the top stories to read ahead of Monday's trading:

London (UKX) -0.49% to 8,642, pulling back after a 1.5% weekly gain. Germany (DAX:IND) -0.23% to 23,710, easing after last week's gains, as investors weighed economic and geopolitical risks. France (CAC:IND) -0.