LONDON (Reuters) – British foreign minister Boris Johnson will travel to Moscow later this year to discuss international security issues, the British government said on Friday.

Johnson cancelled what would have been the first visit to Russia in five years by a British foreign secretary in April due to a poison gas attack in a rebel-held area of Syria that prompted the United States to carry out missile strikes. Moscow backs Syrian government forces against rebels in the country’s civil war.

Russian Foreign Minister Sergei Lavrov subsequently met Johnson at the United Nations in September.

“Our relationship with Russia is not straightforward,” Johnson said in a statement. “That is all the more reason to be talking to Russia – to manage our differences and cooperate where possible for the security of both our nations and the international community.”

Relations between Britain and Russia have been strained since the murder of ex-KGB agent Alexander Litvinenko in London in 2006, a killing which a British inquiry said was probably approved by President Vladimir Putin.

Britain’s foreign ministry said Johnson, on his Moscow visit, wished to discuss North Korea, Iran and regional stability in the Middle East, as well as security for the 2018 World Cup soccer tournament in Russia.

“We will continue to challenge Russia’s approach where we disagree, whether that is Russia’s actions in Syria or its aggression towards Ukraine. My visit will provide an opportunity to talk about these issues and more, face-to-face,” Johnson said.