ANKARA, Sept. 30 (Xinhua) -- A rare official visit by the Turkish president to Germany after four years of strained relations showed that both Ankara and Berlin have to maintain cooperation in areas of economy, energy and security despite disagreements.

"The visit is a very crucial step for normalization of relations between Turkey and Germany. The two countries have serious differences, as we have seen during the joint press conference on the issue of (the Turkish journalist) Can Dundar, but on the other hand, they have interests and issues that oblige them to come together and work together," said Enes Bayrakli, director of European Studies at the Foundation for Political, Economic and Social Research.

The Trump administration is "rude" in transatlantic relations and a trade war is about to start between the United States and Europe, which requires a mandatory cooperation between Turkey and Germany, Bayrakli noted.

"Turkey and Germany have to cooperate due to the fact of the recent crack in transatlantic relations," said Bayrakli .

After four years, Turkish President Recep Tayyip Erdogan paid a state visit to Germany on Sept. 27-29 to restore deeply eroded relations and boost economic cooperation.

Ties between Turkey and many of its Western allies, including Germany, experienced ups and downs in the past few years, and were further eroded after a failed coup attempt against Erdogan in 2016 which caused mutual distrust.

German Chancellor Angela Merkel should first convince her public to normalize ties with Turkey because the main problem is an anti-Turkey campaign conducted in Germany, Bayrakli said.

Longstanding differences on press freedom in Turkey and German citizens imprisoned in the country became a focus at the joint press conference of Erdogan and Merkel on Friday.

"I consider the visit very important because when there are differences, a personal meeting is vital to resolve them," Merkel said, adding that there's a "shared strategic interest in good relations."

But there are also "profound differences" about what constitutes "a free, democratic, open society," she noted.

Merkel called on the Turkish government to resolve the cases of the jailed Germans as soon as possible, while Erdogan repeated that everyone should respect the Turkish judiciary.

In his interview with the Turkish press after the meeting, Erdogan said he told Merkel that the two countries should focus on common interests and put disagreements aside.

For Germany, there are three key issues in relations with Ankara: "the fight against terrorism, the Syrian refugee issue and German investments in Turkey," the Turkish president noted.

Merkel also proposed expanded economic cooperation with Turkey, with a German-Turkish commission to hold its first meeting and her economy minister to visit Turkey in October.

Germany is Turkey's largest trading partner and the two countries have remarkable potential as German businessmen are interested in investing in Turkey, said Bayrakli.

The visit comes at a time when Erdogan aims to thaw ties with both the United States and Germany, according to daily Hurriyet commentator Sedat Ergin.

The main reason for this mindset change is due to the "turbulence in Turkish economy," since the Turkish president believes his country could not tackle this recession if it enters a financial and economic war with the Western world, Ergin explained.