By Amrith Ramkumar

Investors are bracing for more defaults and disruptions in emerging markets after Argentina's deal with creditors highlighted the pandemic's stress on many developing economies.

The agreement to grant debt relief to Latin America's third-biggest economy eased some concerns about a prolonged dispute between Argentina and its creditors. But it also underscored the hardship caused by the coronavirus in emerging markets. Ecuador and Lebanon have also sought concessions from creditors this year, with shutdowns to stop the pandemic and tumbling commodities prices denting developing economies.

Many of these emerging markets are saddled with billions of dollars in debt and rely on tourism and exports to support economic activity. The pandemic is still spreading in many of them, threatening to make the economic fallout last longer than analysts had anticipated.

Tuesday's moves underscored those challenges, even though strength in China and a weaker dollar have generally boosted emerging markets recently. Many emerging-market currencies fell against the dollar, with the beaten-down Argentine peso inching lower, while the Chilean peso and South African rand each slid more than 1%, paring some of their recent rebounds. The Mexican peso also fell.

Concerns about Turkey's economic outlook and the country's options to support its currency have also stoked fresh volatility in the lira recently. The country's central bank has already used much of its foreign-exchange reserves to boost the currency, leaving the government with little room to maneuver.

The moves Tuesday also exemplify the recent divide in overseas markets between countries that are more reliant on tourism and commodities to generate revenue and those that have burgeoning technology industries like South Korea. Investors expect that bifurcation to continue, potentially posing a challenge for those who had rushed into emerging markets in recent years seeking faster economic growth and greater returns.

"It's going to be somewhat from that theme, and there are just some countries that have debt dynamics that are too high," said Jeff Grills, head of emerging-markets debt at Aegon Asset Management.

While the iShares MSCI Argentina & Global Exposure ETF tracking shares of companies that do business in the country rose Tuesday, comparable ETFs for Brazil and Mexico fell with investors still skittish about the outlook for Latin American economic growth.

Analysts say coming talks between Argentina and the International Monetary Fund following the deal with creditors could stoke more volatility in emerging markets.

Argentina owes the IMF $44 billion, and investors say talks about a bailout from the fund could involve economic overhauls that might be unpopular in the country under President Alberto Fernández, a member of the nationalist Peronist movement who partly owed his election victory to mistrust of the IMF.

"Argentina has still got a tough task ahead of it," Mr. Grills said.

Traders say the performance of the U.S. dollar will be a key factor in determining the performance of emerging-market investments after the currency tumbled in July.

A weaker dollar makes it easier for emerging markets to service their dollar-denominated debt, and it boosts commodities prices by making dollar-denominated raw materials cheaper for overseas investors.

The ICE Dollar Index, which tracks the dollar against a basket of major currencies, has edged higher so far this week, dragging some emerging-market assets lower Tuesday despite some of the optimism about Argentina's debt deal.

"We're seeing some residual effects from what's happening with the dollar," said Mohit Bajaj, director of exchange-traded fund trading solutions at WallachBeth Capital.

If the dollar strengthens and limits the recovery in raw-materials prices, analysts say the outlook for emerging markets could grow even more grim. Brent crude futures, the global gauge of oil prices, have hovered in the mid-$40s a barrel recently, staying well above their low point hit in late April but remaining below levels needed to support the budgets of key producing nations such as Saudi Arabia and Nigeria.

Coronavirus-related disruptions to commodities production around the world is also a continuing challenge for many countries. Mining operations in countries such as Peru, Chile and Mexico have been affected by the pandemic in recent weeks, supporting prices for some industrial materials like copper but potentially limiting the amount of revenue that projects in the nations generate.

Some investors had hoped the economic damage from the virus would be short-lived, but a recent surge in cases in the U.S. and many emerging economies is dulling hopes for a swift rebound in growth-sensitive industries such as mining and tourism. That trend is pushing investors to favor sectors like technology that have more attractive prospects, with billions of people generally staying at home and limiting leisure travel.

Analysts say that preference will likely keep fueling the performance gap in assets around the world, even in emerging markets.

"The big question is, 'Does the country have a developed technology sector?" said Yousef Abbasi, global market strategist at StoneX Group.

Write to Amrith Ramkumar at amrith.ramkumar@wsj.com