Ukrainian President Petro Poroshenko said that more than 9,000 Russian soldiers were currently backing up pro-Moscow fighters in the separatist east of the country.
"We have more than 9,000 troops of the Russian Federation on my territory, including more than 500 tanks and heavy artillery and armed personnel carriers," Poroshenko told the World Economic Forum in Davos.
The pro-Western leader stressed there was no military solution to the brutal nine-month conflict that has killed more than 4,800 people and brought Ukraine's economy to its knees.
But he insisted that the key to peace was held by Russia a country that has firmly denied supporting the insurgents despite NATO satellite imagery purporting to show its forces' presence in Ukraine.
"The solution is very simple. Stop supplying weapons. Stop supplying ammunition. Withdraw the troops and close the border. A very simple peace plan," Poroshenko said to a round of applause.
Poroshenko elected in May on a promise to bring his ex-Soviet republic under the military protection of NATO and within the 28-nation EU repeated his urgent call on Western powers to supply Ukraine with modern weapons that could ward off a Russian attack.
"We have a very strong army to defend our territory. But defensive technology is also the things which we need, because only a strong army can help us keep the territory," he said in English.
"Political, economic, defensive and moral support these are the four key ingredients for supporting Ukraine," said the 49-year-old leader.
Poroshenko's previous appeals to US President Barack Obama to supply Ukraine with offensive weapons have been rebuffed by a White House concerned that such deliveries would lead to only more problems with Russia.
The United States and some NATO member states have been supplying Ukraine's cash-strapped forces with military equipment such as night vision goggles and armour.
But Poroshenko insists that more equipment is needed to help soldiers quell the eastern revolt.
Ukraine's economic problems caused by extra war spending and the eastern region's industrial collapse were last year compounded by a months-long cut off from Russian gas supplies.
The dispute stemmed from a disagreement over prices.
Kiev accused Moscow of using gas as a means of "economic agression" and refused to pay the higher rates Russia slapped on Ukraine in the wake of last February's ouster of a Kremlin-backed president.
