Although US Congress passed a legislation to end the government's partial shutdown and raise the debt ceiling, negative spillover effects of the country's fiscal gridlock have now materialized, an expert said.

Wrapping up weeks of bitter fiscal fighting and 16 days of federal government shutdown, US Congress on Wednesday night approved a deal to fund the government through to Jan. 15, and raise the debt ceiling until Feb. 7.

The deal has staved off a default, but has not removed fiscal uncertainty, Hung Tran, Executive Managing Director at the Institute of International Finance (IIF), told Xinhua in a recent interview.

Tran said surging yields for US Treasury bills illustrate the situation. Rates on three-month Treasury bills jumped to 0.35 percent on Wednesday from around 0.03 or 0.05 percent, as market participants were reluctant to accept Treasury bills matured in late October and early November as collateral amid debt default worries.

After the short-term deal reached by the US Senate and the House, one-month and three-month Treasury bill rates edged down to normal levels. However, one-year Treasury bill rate remained high, at around 0.15 percent, which means market participants are still concerned about US budget policy, he explained.

Chief executive officers of financial institutions had expressed concerns about any potential risk of the technical default of US government obligations. The risk was "serious and unthinkable" and might bring "significant damages" to the infrastructure of the US financial system and the global economy, Tran said in the 2013 IIF Annual Membership Meeting held last week.

He said US consumers might not feel comfortable enough to spend because of the ongoing fiscal uncertainty. Retailers are also very nervous about the upcoming holiday season, which includes Thanksgiving, Christmas and New Year's Day, and usually accounts for 20 to 25 percent of the whole year's retail spending.

Many market participants estimated that the fiscal impasse has already shaved 0.5 percent off this year's fourth-quarter growth, he noted.

Tran said the US government's failure to address fiscal policies in an orderly way has disappointed the international community.

"The reputation of the US has suffered. The longer the impasse goes on, the more reputation will be under stressed," he added.

Tran believed it was the right decision for the US Federal Reserve to delay the first reduction in its bond purchases in its September policy meeting, as the fiscal gridlock had rattled financial markets and weighed on the US economy in the past few weeks.

He also said the Fed's tapering decision on its monthly bond purchases is "data dependent" rather than "date dependent," which is driven by the condition of the US economy without a fixed calendar schedule.

Tran believed the US holiday season is a good barometer for the Fed to assess the situation. He said the Fed should not change its monetary policy until the fiscal prospect is clear.