U.S. Secretary of State John Kerry said Tuesday that he and his Russian counterpart Sergei Lavrov have agreed to step up intelligence sharing over the Islamic State (IS) group.

"I suggested to Foreign Minister Lavrov that we intensify intelligence cooperation with respect to ISIL and other counter-terrorism challenges of the region and we agreed to do so," Kerry said using an alternative name for the IS jihadists. 

Iran's foreign minister said Tuesday "numerous questions" remain in talks with world powers aimed at breaking a deadlock in nuclear negotiations, as a delegation he led held fresh discussions with U.S. and EU representatives in Vienna.

The two sides have just six weeks before a November 24 deadline by which they are meant to come up with a final accord aimed at reducing fears Iran's nuclear program could be used to make atomic weapons, in exchange for lifting harsh Western economic sanctions.

Russian President Vladimir Putin on Tuesday praised growing economic ties with "natural ally" Beijing as he hosted Chinese Premier Li Keqiang for high-profile talks.

Li's three-day visit to Russia comes as the Kremlin is locked in a battle of wills with the West over Ukraine and is seeking to ramp up cooperation with Asia and Latin America.

The European Union told Belgrade on Tuesday it should prove its credentials as a future member during an upcoming visit by Russian President Vladimir Putin to Serbia, a historic Moscow ally.

The EU has declared Putin persona non grata for his role in the Ukraine crisis but he can still count on a warm welcome Thursday in Belgrade, which has refused to emulate the tough sanctions imposed on Russia by Brussels.

A U.S. warship docked in Georgia's Black Sea port of Batumi Tuesday, the U.S. embassy said, as tensions in the region remain high over Russia's role in the conflict in Ukraine.

The arrival of the USS Mount Whitney for a five-day visit "reaffirms the United States' commitment to strengthening ties with NATO allies and partners like Georgia," the U.S. embassy said in a statement.

Russian Foreign Minister Sergei Lavrov struck a defiant note on Tuesday, saying Moscow was not planning to buckle to Western demands to ease sanctions over its handling of the Ukraine crisis.

Speaking ahead of key talks with U.S. Secretary of State John Kerry later Tuesday, Lavrov indicated however that Russia was open to mending fences with the European Union.

Ukraine's new defense minister vowed on Tuesday to build an army capable of withstanding Russia as sparks flew in advance of talks between Moscow and Washington over their worst standoff since the Cold War.

Pro-Western President Petro Poroshenko turned to the popular head of Ukraine's frontline forces in his search for the fourth defense chief since Russia's seizure of Crimea in March and the subsequent separatist uprising in the east.

Lithuania on Monday announced a new rapid reaction force designed to meet what it termed new unconventional security threats highlighted by the Ukraine crisis.

The Baltic nation's top general said 2,500 troops will be on high alert as of November to counteract so-called "hybrid warfare" involving unconventional attacks by unmarked combatants, like those in eastern Ukraine.

Dutch officials on Monday returned to the crash site of flight MH17 in eastern Ukraine where the search for remains and belongings resumed despite sporadic exchanges of fire.

The Dutch were part of an Organization for Security and Cooperation in Europe (OSCE) team that has brokered a return to where the Malaysia Airlines Boeing 777 crashed in rebel-held territory on July 17.

Ukraine's President Petro Poroshenko on Monday turned to the head of his frontline forces to become his new defense minister ahead of a crunch general election and high-stakes talks with Russia.

The pro-Western leader asked National Guard irregular forces commander Stepan Poltorak to become Ukraine's fourth defense minister since Russia's seizure of Crimea in March and subsequent separatist uprising in the east.