Anger toward Mr. Karzai is audibly rising in the capital, with many criticizing him for digging in his heels and putting badly needed financial aid in jeopardy.

After Mr. Karzai rejected instructions from a gathering of Afghan leaders, the loya jirga, to sign the deal last month, visits by the American national security adviser, Susan E. Rice, and the special representative for Afghanistan and Pakistan, James F. Dobbins, failed to make any headway. American officials have warned that they are beginning to plan for the possibility of a total and final troop withdrawal by the end of 2014, which would probably jeopardize most if not all international aid.

“He is wasting the time of the nation, and the nation is paying the price,” said Abdullah Abdullah, a presidential candidate in the 2009 and the 2014 elections, referring to Mr. Karzai and the higher cost of goods in the country. “Uncertainty is the worst thing you can impose on a country, especially at a time when we need to focus on the way forward.”

Mr. Karzai says it is the Americans who are undermining the economy. In an interview published in Le Monde on Tuesday, he accused the United States of “psychological war against our economy, in encouraging businesses to leave Afghanistan, in encouraging capital to leave Afghanistan, in terrifying the Afghan population about the consequences of 2014.”

The economy was already slowing. Growth this year has slowed substantially, from about 14 percent in 2012 (thanks to a huge agricultural harvest) to an estimated 3.1 percent this year, according to the World Bank. New business registrations have dropped from 3,500 in the first half of 2012 to 2,000 during the same period in 2013.

But the impasse has added a more immediate layer of uncertainty. Currency exchangers, fearing that the once-stable afghani will continue its slide if the deal is not completed, have started hoarding dollars.

In the hopes of preventing an economic collapse, business leaders have been lobbying the government to sign the deal, known as the bilateral security agreement, or B.S.A.