Chile and Bolivia renewed their wrangling over border disputes Monday as Santiago insisted it had done its part to improve Bolivia's sea access while La Paz derided the work as "far from perfect."

At the Community of Latin American and Caribbean States (CELAC) Summit here, Chilean President Sebastian Pinera said his country has built a railway linking seaport Arica and the Bolivian border obliged by a border treaty reached by Chile, Bolivia and Peru in 1904 to end their 21-year-long war.

The treaty landlocked Bolivia as it allowed Chile to annex a vast expanse of land that gave Bolivia access to Pacific Ocean.

Pinera also said Chile rebuilt the railway in 2005 and has now given Bolivia full access to seaports Antofagasta and Arica with preferential terms, and was prepared to give Bolivia access on similar terms to more ports including Iquique.

The preferential terms include "a year of free warehousing for Bolivian exports and several months free for imports," Pinera said, adding that "Chile will also offer facilities so that Bolivia is able to make the best possible use of its natural gas."

Pinera said he agreed that any treaty could be improved, but "Chile is not willing to reduce or divide its territory."

In response, Bolivian President Evo Morales ridiculed, "I congratulate him on recognizing that the treaty can be perfected, because it is far from perfect." Pinera should visit the railway line he mentioned, Morales added.

Morales also described Chile's ownership of formerly Bolivia's coastline as "internal colonialism."

Repeatedly dubbing the 1904 treaty as "unjust and imposed by force," Bolivia has never ceased its efforts to regain the Pacific coastline, complaining that the lack of sea ports has held back its economic development.

Bolivia, the second largest gas producer in South America after Venezuela, exported 13.2 billion cubic meters of natural gas in 2011, nearly five times the amount 10 years ago.