Bush said that his country was ready to discuss in detail U.S. plans to deploy elements of its missile shield in Europe, which have provoked concerns among the Russian authorities.
Washington has announced its intention of deploying elements of its missile shield in Poland and the Czech Republic, citing possible threats from Iran or North Korea as a reason for the program, and will soon begin consultations with these countries.
On Wednesday, the Czech government confirmed that it will begin official talks with the U.S. on the deployment of the system on its territory. The negotiations will start as soon as possible, and will last through to the end of 2007.
Russian Foreign Minister Sergei Lavrov said earlier Moscow will be guided by a principle of "reasonable sufficiency" in its response to U.S. missile shield plans in Europe, adding that Washington had so far failed to offer a clear explanation of its hasty unilateral efforts.
Putin and Bush agreed to continue regular dialogue on the issue at all levels.
The two leaders also discussed the Iranian problem and said a new UN Security Council resolution on Tehran ruled out any use of force.
Last week the 15-nation UN Security Council voted to introduce additional sanctions against Iran over its failure to meet the requirements set in December's resolution and give up nuclear research.
The new UN resolution gives Tehran 60 days to suspend those elements of nuclear research, which have nothing to do with energy generation, and to resume negotiations. After the deadline expires, the UN Security Council will return to the issue.
Iran responded by saying it would reduce cooperation with International Atomic Energy Agency (IAEA) inspectors until its nuclear file was returned to the agency from the UN Security Council. President Mahmoud Ahmadinejad said Sunday the resolution would not stop his country's nuclear program "for a second."
The new sanctions against Iran, which is suspected of pursuing a covert weapons program, stipulate freezing accounts of 13 companies and 15 individuals associated with Iran's uranium enrichment program and development of missile carriers.
The sanctions also bring in visa restrictions, an embargo on weapons exports from Iran and recommendations to others nations to refrain from selling arms to Tehran or providing loans.
In the telephone conversation, which was held on the initiative of the U.S. side, Putin confirmed that Russia favored a resolution on the Kosovo problem which was acceptable to both Kosovo and Pristina.
Lavrov said Tuesday Russia will demand inquiries into the implementation of all previous UN resolutions on Kosovo if the UN Security Council approves UN special envoy Marti Ahtisaari's plan on the status of Kosovo.
Ahtisaari has proposed that the province be granted internationally supervised sovereignty, but Serbian authorities have strongly opposed the plan as a threat to Serbia's national sovereignty and territorial integrity.
On Monday Ahtisaari returned his proposals on the future status of the breakaway Serbian province to the UN Security Council following fruitless top-level talks in Vienna between Pristina, Belgrade and the European Union, which said later in a statement that it fully backed Ahtisaari's plan.
Serbia's predominantly ethnic Albanian Kosovo province, which has a population of two million, has been a UN protectorate since NATO's 78-day bombing campaign against the former Yugoslavia ended a war between Serb forces and Albanian separatists in 1999.
