At a press conference in Kyiv on March 8, Deshchytsya urged Russia to allow international observers from the Organization for Security and Cooperation in Europe (OSCE) and other organizations into Crimea to monitor the situation there.
One day earlier, armed pro-Russian militias blocked the OSCE mission from entering Crimea for the second day in a row.
The OSCE has said the mission will make another attempt to enter Crimea within hours.
Deshchytsya emphasized that Kyiv invited the mission to monitor the overall situation in Crimea and not to oversee the March 16 referendum there on joining Russia, which Kyiv insists is illegal.
"We consider this referendum and the decision illegal and there is no other way how to protest but to say to the international community that the results will not be valid," Deshchytsya said. "And it is part of the democratic principles if the elections, or referendum at this moment, is not free and fair, then not only Ukraine but the international community will not recognize it."
The Crimean parliament has already approved the move, which has been roundly condemned in Brussels and Washington as illegitimate and a violation of Ukraine's constitution.
Deshchytsya added that the interim government continues to hope for good relations with Russia.
"The Ukrainian government and I think the Ukrainian people also perfectly understand that good neighborhood relations are key for the security in the region," Deshchytsya said. "And we would like to keep such good neighborhood relations with all of our neighbors including Russia. That's the reason why we still keep an option for diplomatic dialogue."
Also on March 8, Ukraine's border guard service reported that "Russian troops" had stormed a border post at Shcholkine in eastern Crimea. The Ukrainian guards and their families were reportedly forced out of the building and an unknown quantity of weapons were seized, according to the statement.
Meanwhile, Russian Foreign Minister Sergei Lavrov told journalists in Moscow that Russia has no direct role in the crisis in Crimea.
He also said the government in Kyiv "is not independent" and "depends, unfortunately, on radical nationalists."
Lavrov also accused Kyiv of barring Russian journalists from entering Ukraine, saying it was a flagrant attack on freedom of information.
In a telephone conversation on March 7 with U.S. Secretary of State John Kerry, Lavrov warned against "hasty and reckless steps" that could harm Russian-American relations.
His comments come after Gazrpom threatened to cut gas supplies to Ukraine if Kyiv fails to pay its gas bill soon.
The head of Gazprom, Aleksei Miller, said Ukraine now owes the gas giant some $1.89 billion.
Also on March 8, Russian news agencies quoted an unnamed Defense Ministry source as saying Moscow is considering a freeze on U.S. military inspections under the START nuclear arms treaty and the 2011 Vienna agreement on confidence-building measures with NATO.
There was a tense standoff late on March 7 between pro-Russian militia and the Ukrainian military at a Ukrainian missile-defense post in Sevastopol.
No violence was reported and the militia later left the base.
"They intruded from both sides," Ukrainian base commander Lieutenant Colonel Vitali Onyschenko said of the attack. "The territory of the army base is big. One truck came from the side of the checkpoint and another one came from the munitions gate. Groups of people, from 35 to 60 people, intruded by breaking these gates and also over the fence. They warned us they could use firearms. We stopped them with some special means and they have now surrounded the command post and they also took control of the duty office building."
U.S President Barack Obama discussed the Ukrainian crisis with German Chancellor Angela Merkel in a telephone call late on March 7. The White House said both agreed on the need for Russia to pull back its forces from Crimea.
China has called for calm and restraint, saying that the issue should be resolved through talks and political means.
Foreign Minister Wang Yi on March 8 urged all parties to keep in mind the fundamental interests of all ethnic communities in Ukraine and interests of regional peace and stability.
Pro-Russian forces have been occupying the peninsula since February 28.
Early on March 8, a spokesman for Vladimir Putin said Russia's president had "not yet exercised" his "right" to use military force in Ukraine.
Speaking on Russian television, Dmitry Peskov acknowledged only that Russia was protecting its military facilities in the Ukrainian region of Crimea.
He repeated Putin's policy that Russia could not "just look on" when "deadly danger" threatened Russians "anywhere in the world."
Peskov added that Russia "fully understands" the concerns of ethnic Russians in eastern and southern Ukraine.
"You don't even have to try to imagine what happens tomorrow if those who were standing behind the coup in Kyiv get to the east or to Crimea," Peskov said. "It seems to me they won't be satisfied with simply pressuring those activists who protested against them."
On March 7, the head of Russia's upper house of parliament said after meeting visiting Crimean lawmakers that Crimea had a right to self-determination and ruled out any risk of war between "the two brotherly nations."
On March 6, Obama ordered U.S. visa bans and asset freezes against so far unidentified people deemed responsible for threatening Ukraine's sovereignty.
The European Union, Russia's biggest economic partner and energy customer, adopted a three-stage plan to try to force a negotiated solution but stopped short of immediate sanctions.
On March 7, the Russian Foreign Ministry responded angrily, calling the EU decision to freeze talks on visa-free travel and on a broad new pact governing Russia-EU ties "extremely unconstructive." It pledged to retaliate.