BERLIN, June 15 (Xinhua) -- Wolfgang Schaeuble, German ex-finance minister and current parliamentary president, has been asked to resolve an escalating conflict between the ruling Christian Democratic Union (CDU) and Christian Social Union (CSU) parties over refugee policy, the newspaper "Rheinische Post" reported on Friday.

The CDU and CSU have reached a political impasse over the question of whether or not to turn back asylum seekers at the German border who were already registered in another Schengen area country. According to a widely-cited report by "Rheinische Post", the 75-year-old veteran politician is now seen as a potential interlocutor between the two conservative sister parties, given his long-standing allegiance to chancellor and CDU leader Angela Merkel on the one hand, and his rhetorical support for a stricter immigration regime on the other.

As recently outlined in an "migration master plan" drafted by Interior Minister and CSU leader Horst Seehofer, the CSU wants to refuse asylum access to German territory if they have already formally entered the Schengen zone via another country.

By contrast, Merkel has warned of a resulting domino effect as Germany's neighbors rush to shutter their internal Schengen borders and is calling for a joint European solution to the "refugee crisis" to be reached within the next two weeks.

Following several failed attempts to reach a compromise within the CDU/CSU parliamentary faction, the CSU has given Merkel an ultimatum until Monday to surrender her opposition to the "migration master plan" before the party takes unilateral action on the issue.

While the interior minister can technically enact some policies related to immigration and asylum without the chancellor's consent, such a move would mark an unprecedented show of disobedience within a German government. Merkel could in turn respond by stripping Seehofer of his cabinet position, raising the possibility of a violent unravelling of the grand coalition formed by the CDU, CSU and German Social Democrats (SPD).

Speaking to the public broadcaster "ARD" on Thursday night, Markus Soeder (CSU), the governor of the CSU's Bavarian home state, defended the aggressive approach adopted by his party as being necessary in order to prevent a repeat of events at the height of the "refugee crisis" in 2015 when large numbers of asylum seekers arrived in Germany.

Soeder said that the CSU would rather countenance a collapse of the federal government in Berlin than "lose credibility".

The CSU is currently trying to fend off a challenge from the Alternative for Germany (AfD) party in looming regional elections in Bavaria. As a consequence, some observers have attributed the heated rhetoric on refugee policy to the CSU's need to attract votes and downplayed the risk that the stand-off between Seehofer and Merkel would result in any permanent damage to the "grand coalition".

Daniel Guenther (CDU), the governor of Schleswig-Holstein, admitted that the ongoing conflict was "substantial" but expressed confidence that the political "family" formed by the CDU and CSU would ultimately remain united.

The CDU parliamentary delegate Christian von Stettner proposed to solve the issue by simply allowing a free vote on the "migration master plan". Von Stettner argued that European solutions had been already been debated unsuccessfully for over two years and that a majority of CDU and CSU delegates consequently supported Seehofer's more restrictive position.

However, the United Nations High Commissioner for Refugees (UNHCR) emphasized that Germany would remain bound by international conventions regardless of the final outcome of CDU and CSU wrangling.

"Germany is obligated to assess which country is responsible for individuals who request asylum at the border. At least for the duration of this process, the affected person must also be allowed to stay (in the country)", Director of the UNHCR's German office Dominik Bartsch explained in the newspaper "WELT".

The SPD has so far largely witnessed the swelling conflict between the CDU and CSU from the political sidelines. Justice Minister Katarina Barley (SPD) cautioned in the newspaper "Augsburger Allgemeine" on Friday that her party would only support asylum policies enshrined in the government's coalition agreement and expressed concern over the increasingly "serious situation" in the CDU/CSU parliamentary faction.

A further discussion of refugee policy is scheduled in the federal parliament on Friday. In the meanwhile, the liberal Free Democratic Party (FDP) has signalized that it would be open to a re-launch of the failed "Jamaica" coalition if the CDU and CSU are unable to overcome their differences.

"We liberals are ready", Thomas Kemmerich, leader of the Thuringian branch of the FDP, told Redaktionsnetzwerk Deutschland (RND).?