President Viktor Yanukovych held a meeting with visiting US senators John McCain and Christopher Murphy in Kiev.
Mr Yanukovych is due to make to Moscow next Tuesday to tie up trade agreements with the Kremlin.
The move is to help the distressed Ukrainian economy, but which the opposition fears will slam the door on integration with the European mainstream.
The opposition fear he may take the first steps towards joining a Moscow-led customs union.
Belarus and Kazakhstan already have a customs union with Russia.
Today, Mr McCain addressed Ukrainians camped on Kiev's main square protesting against Mr Yanukovych's U-turn in trade policy.
He condemned the move away from Europe towards Russia saying that Ukraine's destiny lay in Europe and that it would make Europe better.
Senator McCain was joined on stage by Senator Ryan Murphy, the chairman of the Senate's Europe subcommittee and a Democrat.
Mr Yanukovych may be attempting to keep the attention of both Moscow and Brussels to strike as good a deal as possible to handle its huge debt and outstanding gas payments to Moscow.
But it is a hazardous manoeuvre running the risk of alienating both parties.
Opposition leaders called for another mass rally on Tuesday to monitor Mr Yanukovych's trip to Moscow and any deals made there.
Street protests started after the 21 November decision by President Viktor Yanukovych to walk away from a trade pact with the EU at the last minute and seek closer ties with Russia.
The EU said today it was putting talks on hold on the trade and co-operation agreement.
The move is because Kiev had not committed to signing an agreement and because the arguments being made by the Kiev government had "no grounds in reality".
Police violence on 30 November against what was initially a pro-EU demonstration shocked Ukrainians, igniting deep-seated wider anger over corruption and sleaze.
Anti-government protesters show no sign of backing down and vowed to continue demonstrating for a third week in a row.