WASHINGTON, July 21 (Reuters) - The United States and Germany on Wednesday unveiled an agreement on the Nord Stream 2 gas pipeline under which Berlin pledged to respond to any attempt by Russia to wield energy as a weapon against Ukraine and other central and eastern European countries. The pact aims to mitigate what critics see as the strategic dangers of the $11 billion pipeline, now 98% complete, being built under the Baltic Sea to carry gas from Russia"s Arctic region to Germany. read more U.S. officials have opposed the pipeline, which would allow Russia to export gas directly to Germany and potentially cut off other nations, but the Biden administration has chosen not to try to kill it entirely with U.S. sanctions. Instead, it has negotiated a pact with Germany that aims to impose costs on Russia to prevent it from using the pipeline to harm Ukraine or other countries in the region. "The United States and Germany are united in their determination to hold Russia to account for its aggression and malign activities by imposing costs via sanctions and other tools," the two countries said in a joint statement. If Russia attempts to "use energy as a weapon or commit further aggressive acts against Ukraine," Germany will take steps on its own and pushing for actions at the European Union, including sanctions, "to limit Russian export capabilities to Europe in the energy sector," the statement says. "This commitment is designed to ensure that Russia will not misuse any pipeline, including Nord Stream 2, to achieve aggressive political ends by using energy as a weapon," it says. Under the agreement, Germany and the United States supported a 10-year extension of the Russia-Ukraine gas transit agreement, a source of major revenues to Ukraine, that expires in 2024. "Germany has committed to use all of its available leverage to negotiate an extension to the gas transit agreement," a senior State Department official told reporters, on condition of anonymity. German Chancellor Angela Merkel spoke by phone with Russian President Vladimir Putin hours before the release of the agreement, the German government said, saying Nord Stream 2 and gas transit via Ukraine were among the topics. Germany will contribute at least $175 million to a new $1 billion "Green Fund for Ukraine" aimed at improving the country"s energy independence. Reports about the agreement drew immediate jeers from some lawmakers in both Germany and the United States. Republican Senator Ted Cruz, who has been holding up President Joe Biden"s ambassadorial nominations over his concerns about Nord Stream 2, said the reported agreement would be "a generational geopolitical win for Putin and a catastrophe for the United States and our allies." Cruz and other lawmakers are furious at Biden for waiving congressionally mandated sanctions against the pipeline. In Germany, top members of the environmentalist Greens party called the reported agreement "a bitter setback for climate protection" that would benefit Putin and weaken Ukraine.