Albania -- one of the poorest European countries -- recently joined the US president's newly created "Board of Peace" aimed at resolving conflicts.

Kushner plans to transform the uninhabited southwest island of Sazan -- once home to a secret communist military base -- into a luxury tourist destination, estimated to cost around 1.4 billion euros ($1.2 billion).

But 41 environmental groups from 28 countries voiced their concern over the plans in a letter to Albanian Prime Minister Edi Rama and Environment Minister Sofjan Jaupaj this week.

"The project proposes interventions across 45 hectares (111 acres), posing serious risks to the biodiversity and critical habitats of the area," the statement accompanying the letter said.

Sazan and its surrounding waters "provide crucial habitats for some of the world's most endangered marine species", it added.

The NGOs stressed the construction of a luxury resort "poses a serious threat to these delicate habitats" and urged the "immediate suspension of any decisions advancing the project".

Earlier this week, the US president's daughter Ivanka Trump also visited several sites in the Vlora region, where the island is located, accompanied by around 60 architects.

The Trump family has built a massive real estate empire of luxury resorts and hotels around the world.

In December, an investment firm linked to Kushner ditched plans to build a hotel on the site of Belgrade's bombed-out Yugoslav army headquarters.

The move came after Serbia's culture minister was indicted over alleged abuse of office and forgery of an official document that had allowed the removal of the site's "cultural-heritage status".