BRUSSELS, June 24 (Xinhua) -- German Chancellor Angela Merkel struck a cautious note on the migration summit in Brussels Sunday, saying she is in favor of bilateral or trilateral agreements among member states of the European Union (EU) as a way out of the migration crisis.

She made the remarks upon her arrival here at the summit, saying that there is still no solution to the migration problem involving all 28 member states.

Leaders attending the summit will focus on protecting external borders, as well as tackling the secondary movement of migrants within the EU, Merkel said.

The informal summit, convened by European Commission President Jean Claude-Juncker, is expected to lay the groundwork for the formal one slated for June 28-29, when the reform of the Common European Asylum System (CEAS) will feature prominently on the agenda.

The informal summit, aimed at "finding European solutions to the migration and asylum issues", is an open-ended roundtable discussion, following which there will be neither conclusions nor press conference.

Merkel's Christian Democratic Union (CDU) is in a bitter falling-out with its Bavarian sister party Christian Social Union(CSU), whose leader Horst Seehofer, also in the post as interior minister, put forward a plan to turn back asylum seekers who were already registered in another EU state.

Merkel has been under intense pressure to find a European alternative within two weeks to the CSU's plan, which, if adopted, is likely to prompt a domino effect and put the visa-free movement in the Schengen area in jeopardy.

Despite heated political row over migration, the arrivals of migrants or refugees to Europe have been on a downward trend in the past three years.

According to the data of the International Organization for Migrants(IOM), 52,240 migrants or refugees arrived in Europe as of June 20 this year, compared to 186,768 in 2017 and 390,432 in 2016.

The number of migrants dead or missing in their journey crossing the Mediterranean also dropped sharply. Some 934 migrants are confirmed to have died or be missing thus far this year, while the figure stood at 3,116 in 2017 and 5,143 in 2016.

The EU struck a cash-for-repatriation deal with Turkey in March 2016 and engaged Lybian coast guard in cracking down on migrant trafficking, following the peak year of 2015 which saw more than one million irregular migrants flocking to Europe via different routes.