Russia's surprise offer to the United States to cooperate on an alternative missile defence shield is "a constructive signal," DPA QUOTED a German Foreign Ministry spokesman as saying Friday. "We view this as a positive, a constructive signal in the dialogue that could lead to an easing of tension," said Foreign Ministry spokesman Jens Ploetner. President Vladimir Putin made the suggestion to US President George W Bush at a private meeting on the fringe of the G8 summit of leading industrial nations in the German resort of Heiligendamm. The Russian leader has been critical of Washington's plans to deploy the anti-ballistic missile shield in Poland and the Czech Republic, saying it posed a threat to Russia's security. On Thursday, he proposed a joint scheme under which part of the system be based at a radar station in the former Soviet republic of Afghanistan. Bush described the proposal as "interesting" and said the two sides had formed a working group of experts to see how they could cooperate on missile defence. Ploetner cautioned against making hasty judgements on the proposal until it had been examined thoroughly by the US side. The US plans to install a radar-tracking station in the Czech Republic and 10 interceptor missiles in Poland to counter what it sees as a potential threat from rogue states like Iran. Poland and the Czech Republic are former Soviet satellites, but are now members of the European Union and NATO. The controversial US plan will figure in a meeting between Bush and Polish President Lech Kaczynski when the US leader travels to Poland after the end of the G8 summit later Friday.