Tense situation persisted after a short time of clashes between riot police and demonstrators on streets of Mar del Plata, about 400 km south of the capital Buenos Aires on Friday.
Heavily armed police fired tear gas to drive away demonstrators who gathered here to protest against US foreign policy.
Tens of thousands of people were involved in the planned demonstrations. Angry demonstrators set American national flags blazed.
At least one policeman were wounded in the clashes.
US President George W. Bush, arrived here Thursday night, is joining heads of state and government of Americas to have a two- day Fourth Summit of Americas which will be focusing on topics like free trade and fighting poverty.
At least 7,000 policeman have been guarding against riots and terrorist attacks for days.
Source: Xinhua