Kerry is headed to Moscow to discuss Russia's withdrawal from Syria

The world has what may be its best opportunity to end the five-year Syrian civil war with Russia's planned withdrawal and with peace talks resuming in Geneva, US Secretary of State John Kerry said on Tuesday.

Kerry also told reporters he planned to travel to Russia next week to meet Russian President Vladimir Putin to discuss the way forward in Syria, whose civil war has killed more then 250,000 people and driven millions abroad as refugees.

On Monday, Putin called Syrian President Bashar Assad and informed him that Russia would withdraw a large portion of its forces in Syria.

"The task assigned to the Ministry of Defense and the Armed Forces as a whole has been largely accomplished, so I order the minister of defense to begin withdrawing the main part of our military factions of the Syrian Arab Republic tomorrow," Russian news agency Interfax reports.

However, although Russia will remove a majority of its force in Syria, the Kremlin has signaled that it will still continue to carry out targeted strikes in the country against what it has termed terrorist targets.

"Certain positive results have been achieved. A real chance has emerged to put an end to this long-running standoff," Reuters reports Russian Deputy Defense Minister Nikolai Pankov as having said at a mission accomplished ceremony, citing the RIA news agency.

"But it is still early to talk about victory over terrorism," Pankov continued. "The Russian aviation group has the task to continue carrying out strikes on terrorist facilities."

Even so, the Syrian opposition has largely celebrated the Russian withdrawal as a sign that it could pave the way to the end of fighting. An opposition spokesman told reporters after Russia announced its decision that the withdrawal of Russian forces could help usher in a post-Assad Syria.

The United States is less sanguine about the impact of the Russian withdrawal. The White House is monitoring Russia's withdrawal from Syria but it is too soon to tell what impact the move will have on the country's civil war or the region at large, the White House said on Tuesday.

"It's obviously a move that we'll be watching. The earliest indications are that the Russians are following through, but it's still too early to determine on this point what impact it will have on the broader situation," White House spokesman Josh Earnest told reporters at a daily briefing

He added that Russia did not give the United States direct advance notice of its decision to leave Syria.

Russia's airstrikes in Syria largely targeted rebel groups opposed to the Assad regime. Although Russia insisted its strikes targeted ISIS and al-Qaeda linked groups, the Kremlin equally targeted any group that posed a threat to the Assad regime - including rebel organizations that the US was supporting.

(Reuters reporting By Arshad Mohammed; Editing by Jonathan Oatis)