With deficit reduction talks all but dead in Washington and several bond auctions by fiscally shaky governments on the Continent this week, market specialists say the coming days may well be treacherous, especially if legislators in the United States do not agree on a plan to reduce the deficit.

That prospect looked increasingly likely. Despite the occasional sharp sell-off in the markets, investors have mostly been hoping for the best. In the United States, that means a blueprint for savings and a respite from wrangling over government spending, while in Europe the hope is that the European Central Bank will do more to shore up faltering borrowers like Italy and Spain.

But in each case, the likelihood of bad news outweighs the chances of a breakthrough, said Adam Parker, Morgan Stanley’s chief United States equity strategist.

“It should make people nervous,” Mr. Parker said. “There is a feedback loop between Europe and the rest of the world and that can slow growth. And the political polarization in Washington is also worrisome to investors.”