Washington: US President Barack Obama on Friday called his Russian counterpart Vladimir Putin to express his "deep concerns" over Russia's increased support for the separatists in Ukraine.

"The President (Obama) reiterated his deep concerns about Russia's increased support for the separatists in Ukraine," the White House said.

Obama reinforced his preference for a diplomatic solution to the crisis in Ukraine, and the two leaders agreed to keep open their channels of communication, the White House statement said.

Obama also reiterated his concern about Moscow's alleged breach of the 1987 Intermediate-Range Nuclear Forces Treaty, under which the US and Russia agreed not to develop medium-range cruise missiles.

Meanwhile US Vice President Joe Biden spoke with Ukrainian President Petro Poroshenko today regarding the political situation in Ukraine, the Ukrainian government's efforts to ensure unhindered access to the MH-17 crash site, and Russia's destabilizing actions in eastern Ukraine.

Biden also announced approximately USD 8 million in new assistance to the Ukrainian State Border Guard Service, the White House said.

This additional assistance includes engineering equipment for improving infrastructure along Ukraine's borders, transport and patrol vehicles, surveillance equipment to extend the visual range of border security patrols, and small boats to conduct maritime patrol and interdiction operations.

Biden congratulated Poroshenko on the Ukrainian parliament's confidence vote in Prime Minister Yatsenyuk as well the passage of important economic reform bills and the ratification of agreements with Australia and the Netherlands for security personnel to access the MH17 crash site in support of the international investigation.

"Poroshenko informed the Vice President that access to the crash site had been secured both yesterday and today despite continued separatist attacks in the vicinity," the White House said.

"The two leaders also discussed Russia's deeply destabilising efforts to continue supplying weapons to its proxies in eastern Ukraine and the increasing prevalence of artillery and rocket fire coming from the Russian side of the border," it said.

(PTI)