(Reuters) -The U.S. Treasury bought Argentine pesos in the "Blue Chip Swap" and spot markets on Thursday and it continues to monitor all markets, Treasury Secretary Scott Bessent said on Friday.

"Treasury is monitoring all markets, and we have the capacity to act with flexibility and with force to stabilize Argentina," he said in a post on X.

It was the first announcement of participation in the "blue" market, after Bessent previously spoke of buying pesos in the open market.

Both the "blue" peso and the official one weakened on Friday, with the official currency down 2.8% at 1,441 per dollar and the blue inching down 0.3% to 1,450. Peso one-month nondeliverable forwards priced the currency at 1,446, after rising as high as 1,541 earlier this month. Three-month forwards see the peso just below 1,700, according to LSEG data.

Treasury has not disclosed how much it has spent purchasing pesos or whether it will do it on a schedule.