BERLIN, June 18 (Xinhua) -- Chancellor Angela Merkel's CDU party and its sister party CSU convened a special meeting of their respective leadership committees on Monday in a bid to break a cabinet stalemate over refugee policy.

Having set Merkel an ultimatum to surrender her opposition to a "migration master plan" unveiled by interior minister and CSU leader Horst Seehofer, the CSU has downplayed the risk of a collapse of the German "grand coalition" over the issue.

Speaking to the newspaper Frankfurter Allgemeine Zeitung on Monday, Seehofer moderated his own rhetoric by emphasizing the importance of reaching joint resolutions at an upcoming European Union (EU) summit which should ensure the "fair distribution" of asylum seekers in the European Union.

Similarly, CSU deputy leader Manfred Weber expressed optimism that the CDU and CSU would be able to resolve their differences by finding a "shared path" on asylum policy.

Earlier, the CDU and CSU reached a widely-publicized 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.

As outlined in his "migration master plan", Seehofer 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.

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 specter of an unraveling of the grand coalition formed by the CDU, CSU and German Social Democrats (SPD).

Writing in the newspapers of the "Funke" media group, governor of Saarland Tobias Hans (CDU) also warned that an escalation of the spat over migration could "endanger the existence" of the long-standing joint parliamentary faction formed by the CDU and CSU.

Hans made an appeal to reason on all sides involved in the conflict "not to shut the door to a compromise prematurely".

Citing information from senior EU diplomats, the newspaper WELT reported that Merkel is planning to hold a special meeting between the governments, of Germany, Italy, Austria and other states on the sidelines of the upcoming EU summit.

Merkel hereby hopes to win support for a raft of joint asylum policy measures, including an expansion of the mandate of the EU border control agency Frontex.

Nevertheless, the CSU leadership committee was widely expected to give Seehofer the green light to press ahead unilaterally with his "migration master plan" and begin refusing asylum seekers at the German border from a still-undefined date onwards.

According to a poll published by the newspaper "Augsburger Allgemeine" on Monday, the assertive stance adopted by the CSU on asylum policy appears to be bearing fruit for the party in the midst of a regional election campaign in its homestead of Bavaria.

Some 71 percent of respondents in the survey indicated that they were in favor of a clean break between the CDU and CSU if the latter did not get its way on the subject of border control.

At the same time, however, leading representatives of the Free Democratic Party (FDP) and Greens (Gruene) warned in parallel on Monday against a further escalation of the cabinet conflict.

The opposition parties both warned that they would not be available as an "emergency stop gap" to form a new federal government in Berlin if the CDU and CSU proved unable to resolve their differences.