The prime minister, Mykola Azarov, disclosed that the abrupt Ukrainian U-turn on six years of negotiations with Brussels was taken when Putin demanded a say in, and a delay to, the EU accord.
Azarov and EU officials added that the final blow to the pact, touted as historic, came last week when the International Monetary Fund presented very stiff terms for loans to avoid an economic collapse in Ukraine.
These were demands that Kiev felt impossible to meet and that the EU also found too harsh.
Yanukovych and the Russian president, Putin, met secretly on 9 November; then last Wednesday there was a meeting in St Petersburg between Azarov and his Russian counterpart, Dmitry Medvedev.
Azarov said: "The main so-called agreements were not during my visit to St Petersburg, where we were just clarifying the details, but, of course, at the meeting of presidents. The Russian government made it clear to us that signing of an agreement means it would be subsequently impossible to discuss trade and economic relations."
EU officials said on they were disappointed and surprised by the Ukrainian U-turn.
The EU and Ukraine political association agreement, and a free-trade pact, were to have been signed at a special EU summit in Lithuania opening on Thursday.
Brussels has concluded that there will be no last-minute reversal of the Yanukovych decision.
The EU also said that the issue could be discussed with Russia but that there could be no direct Russian involvement in the proposed EU-Ukraine pact.
"I don't think a three-way discussion is particularly productive," said an official involved in organising the summit in Vilnius, the Lithuanian capital.
Yanukovych said that he would attend the summit to explain why Kiev had turned down the deal.
"Today my plans have not changed. I have repeatedly said that I am planning to go to Vilnius," he was quoted by Interfax news agency as saying.
In a television declaration he described the EU aid offer as humiliating.
"We don't have to be humiliated like this. We are a serious country. A European one," he said.
Russian retaliation against Ukraine had entailed almost $7bn (£4.3bn) in lost exports over the past year, Azarov said.
This threatened thousands of jobs, he added, arguing that Brussels should compensate Kiev for the losses.
"There wasn't a single meeting when I did not raise this issue," he said.
"The EU didn't give us any concrete help."
The EU official agreed that the Europe-Russia "tug-of-love" over Ukraine had been costly for the pivotal country of 46 million people straddling the EU and Russian borders.
"It would appear Ukraine lost trade because of actions taken by Russia. We regret the pressure being put on Ukraine because of this process," he said.
The Yanukovych volte-face brought tens of thousands people on to the streets of Kiev and other Ukrainian cities in the biggest anti-government protests since the 2004 orange revolution.
Yulia Tymoshenko, the imprisoned former prime minister and arch-rival of Yanukovych, announced a hunger strike in protest at Kiev's decision.
Her release and departure to Germany, refused by the president, had become a central demand by Europe for the accord to go ahead.
Amid a severe economic crisis the credit ratings of Ukraine have been cut; the country's foreign reserves fell in October to their lowest level since 2006.
Ukraine has been negotiating a $4bn IMF rescue.
The Yanukovych decision brought veiled warnings from Brussels and from Washington of non-support for the IMF package.
But officials in Brussels also complained that last week's letter from the IMF was poorly timed and may have tipped the balance in Kiev's calculations.
Azarov said the IMF demanded increases in heating and hot water rates, and an end to farming subsidies.
"I got the impression the IMF either doesn't understand the economic situation in Ukraine or gives us conditions that cannot be accepted," he said.
Source: The Guardian UK