The move would give Moscow the option of saying there is no need for Crimea to become part of Russia while keeping it firmly within its sphere of influence.
The dispute between Moscow and the West over Crimea is one of the most severe geopolitical crises in Europe since the end of the Cold War. Russian forces have secured control over the peninsula, but Ukraine's government and Western nations have denounced the referendum as illegitimate and strongly warned Russia against trying to annex Crimea.
Backers of voting to split off from Ukraine in Sunday's referendum say becoming part of Russia would return the Black Sea peninsula to its rightful home. Billboards around the regional capital proclaimed "Together with Russia" and street vendors were selling Russian flags to passing motorists.
But Russia's absorbing Crimea would only worsen tensions with the West, and the parliament declaration could put the bid on hold, depending on the outcome of Russian President Vladimir Putin's bargaining with the West.
In Sunday's referendum, the public will be given two options: becoming part of Russia, or remaining in Ukraine with broader powers.
Crimea, where Russia maintains its Black Sea Fleet base, became the epicenter of tensions in Ukraine after President Viktor Yanukovych fled last month in the wake of months of protests and outbreaks of bloodshed.
Kiev-based political analyst Vadim Karasyov said the Crimean parliament's move is "a message to the West that there is no talk about Russia incorporating Crimea."
"It's a tranquilizer for everybody - for the West and for many in Ukraine who are panicking," he said.
Karasyov speculated that Crimea could exist as a "quasi-legitimate" state, while Russia and the West negotiate.
Russia's Foreign Ministry later said in a statement that the Crimean parliament's action was legitimate. "Russia will respect the results of Crimea's referendum that will be monitored by" observers from the Organization for Security and Cooperation in Europe, the ministry said.
U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov spoke by telephone Tuesday at Washington's initiative.
"From the Russian side, the necessity was underlined of taking into complete account the interests of all Ukrainians and all regions in the search for an exit from the crisis and also the respect of the right of the residents of Crimea to determine their fate on their own in accordance with the norms of international law," the Russian Foreign Ministry said.
Kerry "conveyed that, as we often do, there is an off-ramp here," State Departments spokeswoman Jen Psaki said. While Washington respects Russia's interests, they "in no way justify military intervention or the use of force."
Sergei Zheleznyak, a deputy speaker of the lower house of the Russian parliament, rejected proposals to draft new legislation to facilitate Crimea's accession into Russia.
Zheleznyak wouldn't elaborate, and it wasn't clear whether his statement signaled the Kremlin's willingness to relax tensions or was part of legal maneuvering over the annexation plans.
In a sign that some members of Putin's entourage would prefer a negotiated solution to an all-out confrontation with the West, Konstantin Remchukov, the well-connected publisher and editor of the daily Nezavisimaya Gazeta, spoke strongly against annexing Crimea.
Remchukov, who avoids criticizing Putin, said on Ekho Moskvy radio that the move will trigger painful Western sanctions and cripple the Russian economy.
Remchukov said he believes Russia could negotiate a deal that would have the West guarantee the rights of Russian-speakers and ensure its Black Sea Fleet's continuing presence in Crimea. Russia could promise concessions on the Syrian and Iranian crises in response to the Western willingness to respect Russian interests in Ukraine, Remchukov suggested.
Meanwhile, Ukraine's acting president called for the formation of a national guard and for the mobilization of reserves and volunteers into the country's armed forces.
At the same time, acting Ukrainian Defense Minister Ihor Tenyukh admitted that Ukrainian armed forces and equipment were significantly outnumbered by the Russian army and exhorted wealthy Ukrainians to donate money to equip the nation's army.
He said Russia has some 220,000 troops, 800 tanks, 400 helicopters, 150 planes and 60 ships deployed in Crimea and in military exercises near Ukrainian borders, "several times" more than what the Ukrainian army has.
"What secures victory at war is organization, resources, strategy, tactics and fighting spirit. Today, the armed forces only have the latter two elements - tactics and fighting spirit," Tenyukh told parliament.
Ukrainian Prime Minister Arseniy Yatsenyuk, who will fly to Washington to meet President Barack Obama on Wednesday, called on the West to defend Ukraine against a nation "that is armed to the teeth and that has nuclear weapons."
Yatsenyuk asked Russia, the U.S. and Britain to abide by a treaty signed in 1994, in which they pledged to guarantee Ukraine's security in exchange for surrendering its share of Soviet nuclear arsenals to Russia.
"We are not asking for anything from anyone," Yatsenyuk told parliament. "We are asking for just one thing. Military aggression has been used against our country. Those who guaranteed that this aggression will not take place must from the one side pull out troops and from the other side must defend our independent, sovereign state."
Later in the day, parliament passed a resolution calling on the U.S. and Britain to "use all possible diplomatic, political, economic and military measures for an immediate stopping of aggression."
Yanukovych, speaking in the southern Russian city of Rostov-on-Don, repeated Russia's claim that the new Ukrainian authorities are kowtowing to radical nationalists, and posed a threat to Russian-speaking eastern regions.
Yanukovych, who fled last month after months of protests, said he regarded himself as still the legitimate president and would soon return to Ukraine. He urged the country's soldiers not to fulfill the orders of the interim authorities.
The European Union, meanwhile, on Tuesday proposed a package of trade liberalization to support Ukraine's economy, unilaterally abolishing almost all import tariffs on Ukrainian products in a step that is expected to save the country's exporters 500 million euros ($695 million) annually.
The measure comes without asking Ukrainian concessions in return.
The decision still requires approval from the European Parliament and the 28-nation bloc's member states, but that is widely considered to be uncontroversial.
Associated Press writers Maria Danilova in Kiev, Jim Heintz and Vladimir Isachenkov in Moscow, Juergen Baetz in Brussels and Lara Jakes in Washington contributed to this report.