WASHINGTON - US Secretary of State John Kerry on Monday left for a visit to Russia and Italy, with the ongoing conflict in Syria on his top agenda.

In his first visit to Russia since taking office on February 1, the top American envoy will meet with Russian President Vladimir Putin and other top officials to discuss key issues such as Syria, the denuclearization on the Korean Peninsula and the Afghan war, the State Department said.

Differences over Syria, missile defense and human rights have strained Washington-Moscow ties despite efforts to reset relations with Russia by President Barack Obama in his first term.

The violence in Syria came to the fore again in recent weeks following the allegations of the use of chemical weapons in the Arab nation and reported Israeli air strikes on Syrian targets over the weekend.

The Obama administration has been trying to persuade Russia to stop its support for Syrian President Bashar al-Assad, as Washington and its allies are seeking his ouster to make way for a political transition in the Middle East country.

"So this is a time to talk to the Russians to understand that from our side we remain committed, and if they are as well then we need to think about how to work operationally to make that happen," a senior State Department official said.

"I don't know if we will get an agreement or not, but we certainly think it is worth testing and trying to find some ways forward," the official said at a news briefing on Kerry's visit.

Cooperation in counterterrorism is certain to dominate Kerry's talks in Moscow, as two suspects of Chechen descent detonated two home-made bombs on April 15 near the finish line of the Boston Marathon, killing three people and injuring more than 200 others.

Thomas Donilon, Obama's national security advisor, visited Russia last month with a presidential letter for Putin, in which Obama outlined his administration's expectations for US-Russian relations over the next several months and years.

Kerry, who has met with his Russian counterpart Sergei Lavrov multiple times since assuming office, also plans to meet with representatives from civil society during his visit to Russia, the State Department said.

The US Secretary of State will then head to Rome, Italy, on Wednesday, with Syria and Afghanistan again on his agenda, department spokeswoman Jen Psaki said in a statement.

He has scheduled separate meetings with Jordanian Foreign Minister Nasser Judeh and Israel's Justice Minister and chief negotiator Tzipi Livni in Rome to discuss regional issues and the peace process with the Palestinians, Psaki said.