Samba-Panza, a Christian and former mayor of the Central African Republic's capital, Bangui, was appointed in January to lead the country to general elections next year. She took over after Michel Djotodia, a leader from Sunni rebel movement Seleka, resigned.
Louis Michel, president of the European Union's parliamentary assembly on African affairs, said the interim president needs all the support she can get to bring constitutional order back to the Central African Republic.
To not do so, he said in a statement Monday, "would be unpardonable."
Fatou Bensouda, chief prosecutor at the International Criminal Court, opened a preliminary examination into war crimes in CAR last month.
The conflict erupted in March when Seleka overthrew the government by force.
Michel said the interim president's challenges are "gigantic."
United Nations officials worry the CAR conflict is on the verge of civil war. Anti-balaka, a Christian militia, is suspected of committing the brunt of the atrocities in the country.
The European Commission said Monday the crisis was creating regional problems. As of March 10, there were more than 650,000 people displaced internally and close to 200,000 have fled to neighboring countries to escape the violence.