The Slovenia-Croatia border dispute is a bilateral issue, and the European Commission was "crystal clear" in its decision not to get involved in it, the Vice-President of the European Commission (EC), Frans Timmermans, told Slovenia's state agency STA on Tuesday.
Timmermans is the lead candidate of the Party of European Socialists (PES) to replace the current EC president, Jean-Claude Juncker, following the European elections in May.
The Dutch politician and diplomat said in an interview for STA that the Slovenia-Croatia border row is a bilateral issue to be solved by the two EU member countries, and that the arbitration border ruling should be implemented by both parties.
"The Commission was crystal clear about that, and I can't see why someone does not want to understand that," Timmermans was quoted as saying before his official visit to Ljubljana, scheduled for Thursday.
He went on to say that the two parties involved in the case "cannot absolve themselves from the the responsibility for the matter" by passing the problem to the European Commission.
Last year, the Commission refused to join Slovenia's complaint which it had lodged against Croatia, accusing it of violating European laws by refusing to implement the 2017 arbitration ruling which defined the two countries' land and sea border.
Zagreb continues to refuse the arbitration ruling, insisting that the arbitration process had been compromised by Slovenia.
Although Croatia had agreed to settle the dispute by international arbitration before it joined the EU in 2013, Zagreb walked out of the proceedings in 2015 following a scandal in which leaked tape recordings showed that Ljubljana officials had inappropriate contact with an arbitration judge.
Although the judge was later replaced, Croatia refused to get back to the table. Zagreb officially rejects the 2017 ruling, and has repeatedly invited Ljubljana to negotiate the dispute bilaterally again.
Ljubljana, in turn, rejects any more negotiations, considers the arbitration ruling final, and claims that by refusing to implement the border as defined by arbitration Croatia is violating EU law.
"History is for historians"
In his interview, Timmermans also criticised the outgoing President of the European Parliament, Antonio Tajani of Italy, for his recent statement at a memorial ceremony for Italians killed in the aftermath of the World War II by Yugoslav partisans, in which he mentioned "Italian Istria" and "Italian Dalmatia."
Istria is a peninsula in the northern Adriatic which is today for the most part Croatia's territory, with smaller portions of it belonging to Slovenia and Italy. Dalmatia is Croatia's Adriatic coastal region, which used to have a large Italian ethnic minority, which largely left the area in the aftermath of World War II.
Tajani's statement immediately provoked public outcries in both Slovenia and Croatia, with Tajani later sending letters of apology to top officials in Ljubljana and Zagreb, in which he insisted that his comment was "in no way a territorial claim."
Asked whether Tajani's comment was reason enough for his resignation, called for by Social Democrats in Slovenia and Croatia, Timmermans said he would not insist on Tajani's resignation, although he criticised Tajani for "instrumentalising the past" in his speech.
"History should be left to historians," Timmermans said.
Earlier this month, ahead of European Parliament elections in May, the European Socialists (PES) bloc held a congress in Madrid in which they confirmed that Timmermans would be their candidate for president of the European Commission.
A delegation of Croatia's Social Democratic Party (SDP), led by party chairman Davor Bernardic, attended the Madrid congress of PES.