In her congratulatory cable Merkel says she is looking forward to continuing to foster the friendly and partner relations between the two countries with the new prime minister.

She wished Cerar "success, creative strength and a lucky hand" in his responsible job at the time of great challenges, noting that she would be looking forward to welcoming him soon in Berlin.

"The US and Slovenia share a strong partnership grounded in shared values and a mutual commitment to human rights and freedoms," Obama says in his letter, according to a copy forwarded by the PM's office.

Noting Slovenia's contribution to international security through its peacekeeping deployments in Afghanistan and Kosovo, Obama called for building on this foundation through mutual support for Ukraine's sovereignty and territorial integrity.

The US president also called for deepening bilateral economic and commercial ties. "As your government presses ahead with vital economic reforms, expanding our bilateral trade and investment relationship will benefit both the American and the Slovenian people," the letter from Obama reads.

Cerar has also received congratulations from European Commission President Jose Manuel Barroso, as well as from prime ministers of Slovakia, Serbia, Bosnia-Herzegovina, Romania and Hungary and Brazil's president, among others.

Cerar took up his post last week as his centre-left coalition government was endorsed by parliament last Thursday.