BRUSSELS — President Vladimir V. Putin of Russia began his first talks in Brussels on Friday since his reelection earlier this year.
Energy, trade, and Syria were on the agenda, and the discussions were expected to be tense.
Russia is the main external energy supplier to the 27-nation European Union, and Putin is to meet senior officials from the bloc in the 30th summit to take place between the two sides.
In recent years, relations have been soured by disputes over gas pipelines, trade issues, and human rights, and there are sharp differences with the union over Moscow’s support for President Bashar Assad of Syria since the uprising began there in March 2011.
European leaders have criticized Russia over the jailing of members of the female punk band Pussy Riot and new pressure on opposition figures since Putin was reelected.
Putin gave a number of combative performances when he appeared at summits in his previous terms as Russian president, often taking a tough line in private with fellow leaders and sometimes in public with the media.
In 2008, when Putin became prime minister and Dmitry A. Medvedev succeeded him as president, the tone at European summits improved, though the regular meetings rarely produced significant breakthroughs.
After he returned to the presidency, Putin hosted a relatively harmonious meeting in St. Petersburg in June.
‘‘We want to deepen our cooperation at a global level: on challenges such as global economic governance, climate change, or cooperation at the United Nations,’’ said Herman Van Rompuy, president of the European Commission, in a statement before the meeting.
‘‘Together the EU and Russia can make a decisive contribution to global governance and regional conflict resolution.’’
A key issue at the summit is expected to be energy since the European Union nations buy about 20 percent of their natural gas from Russia.
The union is investigating whether Gazprom, the Russian gas export monopoly, violated European antitrust laws by restricting European buyers’ right to sell gas to one another and by linking gas prices to oil prices.
Union authorities can fine companies found in breach of antitrust laws 10 percent of their global annual sales, and they can order companies to change their business practices so they comply with European standards.
Gazprom has strongly contested those claims and has insisted that its pricing practices are in line with the rest of the industry.