The yen has emerged as the weakest Group-of-10 currency in August as the impact of joint U.S.-Japan intervention in the foreign-exchange market fades.

As of Aug. 10, the yen had fallen about 0.5% against the dollar this month, the worst return among G-10 currencies, according to Bloomberg. That has reversed part of the 3.2% gain it posted in July.

The currency briefly strengthened after weaker-than-expected U.S. employment data last week, but soon resumed its decline.

With Japan’s Obon holiday set to thin trading, markets are watching for another round of intervention by authorities. Still, the yen may remain under pressure because the underlying drivers of its weakness — the U.S.-Japan interest-rate gap and concerns about Japan’s fiscal expansion — remain in place despite the joint action.

In a report, Nomura Securities said attention would center on signals from Japanese and U.S. authorities about their willingness to intervene, as well as any related comments, during a period of reduced market participation.

On July 31, the U.S. and Japan jointly bought yen for the first time since 1998 after the dollar-yen rate approached 164. The yen later rebounded to around 155 per dollar, but has since climbed back above 158 per dollar.

Goldman Sachs said the limited market response to the intervention reflected the fact that the root causes of yen weakness remain unresolved. Without changes in global conditions or policy, it said, pressure on the yen is likely to build again over time.

Separately, the Bank of Japan signaled in minutes of its latest policy meeting that upside inflation risks are increasing. Markets are pricing in about a 66% chance of a benchmark rate hike in September, while an increase by October is effectively seen as a done deal.

Bloomberg estimates Japanese authorities spent about $34 billion on July 31 to support the yen. It also estimates about $53 billion was deployed the previous day, which would be the largest single-day intervention on record if confirmed.