Slovenian President Borut Pahor on Thursday gave the anti-migrant SDS party a deadline to clearly state if it can form a coalition government.
In June 3 elections, Janez Jansa's centre-right Slovenian Democratic Party (SDS) won 25 of the 90 seats in parliament, becoming the biggest single party in the assembly.
That was well ahead of the anti-establishment LMS of comedian-turned-politician Marjan Sarec which came second, winning 13 seats.
"In a week's time, he (Jansa) must inform me, whether he accepts the mandate to form a government or not," Pahor told reporters after meeting the SDS leader.
So far, Jansa has only held coalition talks with the other centre-right party in parliament, Nova Slovenija (NSi) which has seven seats, while the remaining centre-left parties -- that together hold 43 seats -- have been holding daily negotiations over a possible six-party coalition led by the LMS.
Such a coalition would also have to include the NSi -- which has attended the negotiations but is still dissatisfied with the conditions -- or leftist Left Party (Levica), whose political programme includes leaving NATO and cutting defence spending.
"A six party (coalition) is theoretically possible but, as a citizen of this state, I would not like to witness or try that in real life," Jansa said.
Jansa said he would see all parliamentary party leaders on Monday to "informally assess the chances of forming a solid coalition".