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.¡±