BARCELONA, June 29 (Reuters) - Spanish Prime Minister Pedro Sanchez met Catalonia"s new pro-independence regional head on Tuesday for the first time as the central government sought to improve ties after pardoning nine jailed separatist leaders. The two agreed that negotiations between both governments on the region"s political conflict would resume in September in Barcelona while acknowledging the significant differences that still remain between them. "This negotiation will not be easy, because we will not give up," Catalan head of government Pere Aragones, who took office last month, told reporters after the meeting in Madrid, adding that any solution reached at the negotiations had to be validated in a vote by citizens. "Let no one be confused: We will approach this with full determination to defend a referendum for Catalonia, and an amnesty," he said, referring to the more than 3,000 separatists currently under legal investigation. read more Sanchez, who opposes independence, had previously ruled out both demands. read more "The government cannot make sense of Catalonia without Spain, or Spain without Catalonia," the central government"s spokesperson Maria Jesus Montero said at a separate news conference, adding that both sides were conscious about their opposing views on the independence issue. An unauthorised referendum on a breakaway in 2017 led to a short-lived declaration of independence and Spain"s worst political crisis in decades. Separatist leaders were convicted and sentenced to lengthy prison terms on a variety of charges. Sanchez pardoned them last week in what he said was a goodwill gesture to kickstart negotiations on the Catalan issue. However, Spain"s Court of Auditors is requesting the return of about 5.4 million euros ($6.43 million) from 40 former Catalan officials due to their alleged role in promoting Catalonia"s independence bid abroad, including some pardoned leaders, according to a court report published by several newspapers on Tuesday. The court has not issued any ruling on the potential misuse of public funds by them but its interim request implies that they need to deposit the demanded amount, according to the reports. If they could not do so, their assets would be seized. A court spokesperson said the document was not public yet. The court requested 1.9 million euros from Oriol Junqueras, the most prominent of the freed politicians for his role as Catalonia"s deputy leader until 2017, according to the reports. Junqueras, the chairman of Aragones" party Esquerra Republicana de Catalunya, told Reuters on Monday that the court is politicised and that its investigation shows "the end of the repression is very far away". read more He said it was essential to approve an amnesty related to the 2017 events. The court also requested 1.9 million euros from former Catalan head Carles Puigdemont, who fled to Belgium after the independence declaration. The government insisted that Puigdemont and other separatists in self-imposed exile should return to Spain where they face an arrest warrant. "People out of the reach of the justice system must come back and collaborate," spokesperson Montero said. ($1 = 0.8402 euros)