Tunisian President Kais Saied on Monday rejected financial support announced by the European Union in September, saying the amount is small and goes against a deal signed three months ago.
Saied's move could undermine the "strategic partnership" from July that includes measures on combating human traffickers and tightening borders, and which came during a sharp increase in boats heading to Europe from the North African nation.
The European Commission last month said it would disburse 127 million euros ($133 million) in aid to Tunisia as part of the deal to fight illegal immigration from Africa to Europe.
"Tunisia rejects what the EU announced, not because of the small amount ... but because the proposal conflicts with the memorandum of understanding signed in July," Saied said.
The July deal included a pledge of 1 billion euros in aid to Tunisia to help its battered economy, rescue state finances and deal with the migration crisis.
The smaller amount announced by Europe 10 days ago, however, has frustrated Tunisian authorities struggling to improve public finances and raised fears among credit rating agencies that the government could default on foreign debts in coming months.
The dispute between the two parties has coincided with the arrival of record numbers of migrants from Tunisia and North Africa to Italy's island of Lampedusa.
Tunisia last week postponed a visit by a delegation from the European Commission to discuss the details of the migration agreement.
Last month it also denied the entry of five members of the European Parliament’s foreign affairs committee for meetings over the political situation in Tunisia, saying it would not allow interference in its affairs.