The announcement by Prime Minister Tony Abbott came just days after Canberra said it would toughen its sanctions against Moscow so they match those of the European Union.
Abbott told parliament uranium sales were on hold until further notice.
"Australia has no intention of selling uranium to a country which is so obviously in breach of international law as Russia currently is," he said.
Australia does not use nuclear power but is the world's third-ranking uranium producer behind Kazakhstan and Canada. In the 2012-13 financial year it exported 8,291 tonnes of oxide concentrate worth more than Aus$800 million (US$743 million).
Japan, the United States and the European Union buy the majority of Canberra's exports of the nuclear fuel, with smaller shipments to Russia, South Korea, China, Canada and Taiwan.
Abbott has used tough language recently against Russia -- particularly since Malaysia Airlines Flight MH17 was shot down over eastern Ukraine in July, killing all 298 on board including 38 Australian citizens or residents.
He added that the government was also considering short-term support to Ukraine through aid and "non-lethal military assistance".
"Australia and Ukraine are geographically distant but we have grown close in responding to the MH17 atrocity in which Australians were murdered, were murdered by Russian-backed rebels," he said.
"In the medium-term, we are considering civil and military capacity-building assistance to that country."
Australia will also open an embassy in Kiev.
The Ukraine crisis will be a key topic during a NATO summit in Wales this week attended by Foreign Minister Julie Bishop.
She said a decision on whether Russian leader Vladimir Putin should be invited to the Group of 20 summit in Brisbane in November was still some way off, as opposition to his presence grows.
Bishop said she would be speaking with NATO members to canvass opinion, but there was time for the Russian president to prove why he should still be at the table.
"But the point is this, there are a number of international meetings before the G20," she said, pointing to the APEC forum in Beijing and the East Asia summit in Myanmar.
"I think we'll have a better idea of the international community's attitude and indeed President Putin's attitude to attending these meetings before we consider the G20."
Bishop added that as the rotating G20 host Australia's role was to "consult and to reach a consensus".
"But we are some way from that decision and of course we take soundings, and I've no doubt people will raise it with me, but it is not Australia's call," she said.
In June Russia was axed from a G7 meeting in Brussels over its annexation of Crimea, with Putin cold-shouldered by the United States and its allies since the March takeover of the peninsula from Ukraine.