Sergei Kislyak, Russia's deputy foreign minister, and Witold Waszczykowski, Poland's chief missile defence negotiator, met on Thursday in Warsaw to discuss the plans.
Kislyak was also due to meet Radek Sikorski, Poland's foreign minister, during his one-day visit to the country's capital.
Washington says the missile defence system is needed to protect the US and Europe from so-called rogue states such as Iran.
Vladimir Putin, Russia's president, has argued that an installation so close to Russia's territory would threaten its security, and has warned that Moscow could target the base with its own missiles.
Tusk, who was in Prague for talks with his Czech counterpart, Mirek Topolanek, said that "an exchange of information and intentions is needed from all those interested in the region.
"We are curious what type of questions and opinions every country in the region has, including Russia."
Poland's interest in the US proposal has further strained its already difficult ties with Russia, and Thursday's meeting is aimed at improving the two countries ties.
Russia's president says an installation so close
to Russia could threaten its security [AFP]
Meanwhile, Topolanek has said Prague could reach an agreement with the US on accepting a radar base as soon as this spring.
He said: "In an ideal case ... we'll be able to submit the treaties to parliament some time after the Nato summit in Bucharest in the course of April or later."
After Poland and the Czech Republic opened negotiations with the US early last year, Topolanek's government has voiced more enthusiasm for the project than that of Tusk.
Asked whether Warsaw wanted to reach a deal before George Bush, the US president leaves office in January 2009, Tusk said: "We are not delaying anything or trying to speed it up. We do not want to wait with this until the change of the US administration.
"We are only saying that, perhaps, if the negotiations do not bring an effect, the timeline will be extended."
Tusk did not elaborate on what guarantees he had in mind, but Poland's defence minister said on Wednesday that Washington should strengthen Poland's short and mid-range air defences by giving Warsaw Patriot or Theatre High Altitude Area Defence (THAAD) missiles.