(Recasts after news conference)
BERLIN, Dec 7 (Reuters) - Germany's Chancellor-in-waiting Olaf Scholz expressed concern on Tuesday about Russian troop movements on the Ukrainian border and said any attempts to cross the frontier would be unacceptable.
"It is very, very important that no one rolls through the history books to draw new borders," Scholz said at a news conference after signing a three-party coalition agreement.
U.S. President Joe Biden is to tell President Vladimir Putin later that Russia faces tough economic sanctions if it invades Ukraine, U.S. officials have said, as thousands of Russian troops mass near the Ukrainian border.
"It must be quite, quite clear that it would be an unacceptable situation if there were a threat to Ukraine," Scholz said, stressing that borders could not be violated.
Scholz, a Social Democrat, is due to take office on Wednesday after being elected by the Bundestag lower house of parliament.
He will head an alliance also including the Greens and the liberal Free Democrats (FDP) that brings to an end 16 years of conservative-led government under Angela Merkel, who did not stand for a fifth term in a September election.
Incoming Vice-Chancellor Robert Habeck, who is co-leader of the Greens, said the Nord Stream 2 pipeline, which is to transport gas from Russia to Europe, bypassing Ukraine, had not yet received approval and political discussions had to continue.
The Greens have traditionally taken a tougher line with Russia, as well as with China.
Asked about China, Scholz said he would consult closely with European partners. He skirted questions on whether Germany would join a diplomatic boycott of the 2022 Beijing Winter Olympics.
"(We) must know our differences and nevertheless get on with each other", said Scholz, appearing to stick closely to Merkel's favoured approach of seeking dialogue.
He praised Biden for strengthening a community of democratic countries, saying his priority would be to work with states sharing the same values and to strengthen the European Union. His first trip abroad will be to Paris.
The Greens' Habeck also said that results of investment in renewable energy would take two or three years to be seen.
The coalition deal, entitled Dare More Progress, aims to accelerate a green transition and modernise Europe's biggest economy as well as introducing some progressive social reforms, such as making dual citizenship easier.
(Reporting by Madeline Chambers and Kirsti Knolle; Editing by Nick Macfie and Angus MacSwan)