The United States and Russia are going through a difficult period but rising tensions between the two fall well short of a new Cold War, US Secretary of State Condoleezza Rice said Monday. "It's a time for intensive diplomacy," she said as she flew here for high-level meetings amid new strains in relations over major policy differences underscored by Russian President Vladimir Putin's increasing criticism of the United States. Rice, who sees Putin on Tuesday, said Washington was committed to working through those differences, notably over US plans for a missile defense system in Europe, Russia's threat to suspend a major military treaty and Moscow's opposition to a UN plan for Kosovo independence. There is also growing US concern about Moscow's treatment of its former Soviet state neighbors and steps Putin has taken to consolidate power in the Kremlin are seen as democratic backsliding as Russia prepares for presidential and parliamentary elections next year. "I don't throw around terms like 'new Cold War,'" Rice told reporters as she flew here. "It is a big, complicated relationship, but it is not one that is anything like the implacable hostility" that clouded ties between the United States and the Soviet Union. "It is not an easy time in the relationship, but it is also not, I think, a time in which cataclysmic things are affecting the relationship or catastrophic things are happening in the relationship," Rice said. She said, "It is critically important to use this time to enhance those things that are going well and to work on those things that are not going well." She noted that the United States and Russia were working together in numerous areas, including on dealing with Iran and North Korea's nuclear programs as well as cooperating in the fight to stop the global spread of weapons of mass destruction and Middle East peace efforts. "Russia is not the Soviet Union, so this is not a US-Soviet relationship, this is a US-Russian relationship," said Rice, an expert on the Cold War who first visited Moscow in 1979. "A great deal has a changed." But her visit comes as the two nations have traded increasingly sharp barbs at each other, despite ostensibly warm personal feelings between Putin and President George W. Bush, who spoke to each other just last week and are expected to meet at a summit of leaders in Germany next month. In April, simmering Russian anger over U.S. plans to place missile defense components in Poland and the Czech Republic, both former Warsaw Pact members, boiled over despite Washington's pledges to cooperate with Moscow on the system and even share technology. Russia views the plan as an attempt to alter the strategic balance, a fear Rice has dismissed as "ludicrous" but top Russian military officials have hinted the system might be targeted. US and Polish officials opened formal talks in Warsaw on the plan even as Rice was headed to Moscow. The two sides were talking about the legal status of a possible US anti-missile base on Polish soil and the American personnel stationed there. Hours before the United States and its NATO allies were to meet in Norway recently to discuss this issue, Putin threatened to suspend Russia's participation in a key treaty limiting military deployments in Europe. Rice said that NATO and the United States want to keep the Conventional Forces in Europe (CFE) pact alive and want to ratify it themselves, but cannot unless Russia honors its treaty commitments. Russia views US activity in its former sphere of influence with growing suspicion and just last week, Putin denounced "disrespect for human life, claims to global exclusiveness and dictate, just as it was in the time of the Third Reich." The Kremlin insisted that Putin had not meant to compare the Bush administration's policies with those of Nazi Germany but the reference appeared to highlight Russia's annoyance at what it sees as US domination of world affairs and meddling in Russian politics. Rice did not address Putin's comments but suggested that sometimes emotionally charged remarks by Russian officials were not constructive, saying she had urged counterparts to avoid "rhetoric that suggests the relationship is one of hostility." She couched criticism of Russia's democratic progress under Putin with a caveat alluding to the country's troubled history - from Czarist empire to communist monolith - a nation now struggling to find its role in the world and at home. "This is a big and complex place that is going through a major historic transformation ... things are not going to change overnight, but frankly we would like to see them change faster than they are changing, and for the better," Rice said. She said she would use her meetings in Moscow to impress on Putin and other top Russian officials the need for a missile defense to counter threats from Iran and North Korea and the genuine US desire to work with Russia in building the system transparently. She also said she would push the Russians on accepting a UN proposal for supervised independence for Kosovo, now a UN-administered province in Russian ally Serbia, that Moscow has threatened to block.