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.

President Petro Poroshenko on Sunday dismissed Ukraine's third defense minister since the March seizure by Russia of Crimea and the subsequent uprising by pro-Kremlin insurgents in the separatist east.

The Western-backed leader's official website said he would nominate a new defense chief on Monday after "accepting the resignation" of Valeriy Geletey.

Russian President Vladimir Putin has ordered his defense minister to pull thousands of troops from the border with Ukraine, ahead of key talks on a fragile truce in the ex-Soviet country.

The announcement by the Kremlin late Saturday comes as the Russian strongman is gearing up to hold the talks with Ukrainian President Petro Poroshenko and European leaders in Milan on Friday, signaling the possibility of shoring up the rickety truce.

Australian Treasurer Joe Hockey confirmed Sunday Vladimir Putin will attend the G20 leaders' summit in November, despite concerns about Russia's actions in Ukraine in recent months.

Australia's confirmation that the Russian leader would attend the high-powered summit came after Ukraine's President Petro Poroshenko said he would also meet Putin next week.

Ukraine's President Petro Poroshenko on Saturday said he will meet with Russia's Vladimir Putin next week as Kiev reported rebel attacks have subsided, signaling the possibility of rescuing a truce in the six-month conflict.

Pro-Russian rebels and the Ukrainian military in the eastern Donetsk region said they have agreed to a no-shooting period, and the army announced "progress" in negotiations and readiness to pull back forces.