Ursula von der Leyen and Pedro Sanchez are expected to promise 200 million euros ($215 million) in aid when they meet President Mohamed Ould Ghazouani in the capital Nouakchott, EU officials said without elaborating.

Migration is set to dominate debate in June's European Parliament elections amid growing anti-immigration rhetoric from right-wing parties.

Mauritania's strategic importance is growing amid an increase in migration pressure and rising instability in the Sahel region, and Spain wants to support it and strengthen ties through the EU, a Spanish government source told reporters.

The number of migrants entering Spain irregularly by sea jumped nearly 300% in January, with the vast majority arriving in the Canary Islands. About 83% of the dinghy boats making it to the archipelago departed from Mauritania, say Spanish officials.

That followed a record number last year who attempted to reach Europe via the Spanish archipelago, located off the African coast.

Spain has deployed police officers in Mauritania since 2006, when a large inflow prompted an overhaul of migration policy to put the focus on giving financial and security aid to the boats' countries of departure.

Spain wants to increase its help to Mauritanian authorities for border security but does not plan to send more police, the government source said.

Mauritania, home to fewer than five million people, suffers from widespread poverty and since 2012 has been dealing with the influx of tens of thousands people from neighbouring Mali.

Security, humanitarian aid, migration programs and economic development will also be on the agenda for Thursday's talks, the Spanish source said.

($1 = 0.9289 euros)