BRUSSELS, Oct 1 (Reuters) - An EU-Ukraine trade deal at the centre of tensions between Russia and the West can only be changed by Brussels and Kiev, the head of the European Commission told Russia's President Vladimir Putin in a letter on Wednesday.
Putin wants more three-way negotiations to amend the EU's accord with Kiev, which Russia says will hurt its own economy, and has threatened to curtail Ukraine's access to Russian markets if Kiev implements the deal.
"In this context, we have strong concerns about the recent adoption of a decree by the Russian government proposing new trade barriers between Russia and Ukraine," Barroso said in his letter, released by his office.
"The Association Agreement (between the EU and Ukraine)remains a bilateral agreement and ... in line with international law, any adaptations to it can only be made at the request of one of the parties and with the agreement of the other," Barroso wrote. (Reporting by Robin Emmott; editing by Adrian Croft)