The yen swung to a loss, sapping momentum from efforts by the U.S. and Japan authorities to boost the currency.

The Japanese currency weakened by 1%, ending the session at ¥159.29 per dollar, marking the worst performance among Group-of-10 peers on Monday. Those declines wiped out half of the yen’s recent intervention rally, a psychologically significant move for traders who remain on alert for further official support.

“Without fresh intervention, it will continue to drift lower,” said Lee Ferridge, a strategist at State Street. “It seems that the market is disappointed that we didn’t see more intervention.”