Talks between a senior US state department official and Argentine President Cristina Kirchner here Thursday were to be dominated by concerns over US reactivation of a navy fleet for Latin America, a government official said.

Argentine authorities "will communicate this concern and ask Washington's envoy to specify the reach of the decision," Deputy Foreign Minister Victorio Taccetti told reporters.

"We are concerned by the subject of the Fourth Fleet. We are concerned because we don't know why it is being reactivated," said Taccetti, speaking ahead of the two-day visit by US Assistant Secretary of State for Western Hemisphere Affairs Tom Shannon.

The fleet, which has a changeable composition of ships, was reestablished on July 1. It last operated in 1950. In the intervening period, it was absorbed by the Second Fleet that patrols the Atlantic Ocean.

Several Latin American nations have said the reactivation was unsettling. Leftist-run states such as Cuba, Bolivia and Venezuela fear the move signals a return to US gunboat diplomacy.

"What reason could the United States have for dispatching such a powerful naval force to a peaceful region?" Venezuelan President Hugo Chavez, a virulently anti-US leader, asked at a regional trade summit last week.

Brazil too has said it is concerned by the decision, prompting the US ambassador to that country, Clifford Sobel, to stress the fleet would not have an offensive role.

"Some see it as a threat," he acknowledged, adding: "This is not true."

The Fourth Fleet will be mainly used for humanitarian assistance missions and to provide support for anti-narcotics operations, while respecting the sovereign maritime territorial limits of countries in the region, he told a business conference in Sao Paulo.

US Admiral Jim Stavridis has said the fleet's reinstatement was a sign of cooperation between the United States and Latin America.

Argentina, under President Cristina Kirchner as well as under her predecessor and husband Nestor Kirchner, has had prickly relations with the United States. Washington fears Argentina may be aligning itself with Chavez.

US allegations in December that Chavez had illegally sent 800,000 dollars to Argentina with a US-Venezuelan businessman to finance Cristina Kirchner's election plunged ties to a new low.

Shannon arrived in Buenos Aires on Thursday, accompanied by senior officials from the US departments of state, justice and defense, and the US treasury undersecretary for Western hemisphere affairs, Brian O'Neill.

Their talks with Argentine government officials will also cover economic issues, including market access, operations of regional trade blocs, biotechnology, as well as fighting terrorism and the struggle against drug smuggling, said the US ambassador to Argentina, Hector Timerman.

Shannon and O'Neil were to speak with Argentine Economy Minister Carlos Fernandez, central bank chief Martin Redrado, Buenos Aires governor Daniel Scioli, Justice Minister Anibal Fernandez and Finance Secretary Hernan Lorenzino.