The agreements on association and free trade, due to be signed at an EU-Ukraine summit on November 28 in the Lithuanian capital Vilnius, offer the former Soviet republic of 46 million people the chance of an historic shift west away from Russia.
But signature hinges on freedom for ex-prime minister Tymoshenko, a fierce opponent of President Viktor Yanukovich.
She was jailed in 2011 for seven years for abuse of office after a trial which the EU says was political.
Irish politician Pat Cox and former Polish President Aleksander Kwasniewski, who have been shuttling between Brussels and Kiev for more than 18 months on a mission to nail down a deal over Tymoshenko, went straight into meetings with officials after arriving in Kiev on Wednesday, EU sources said.
They are due to meet Yanukovich and opposition members and are likely to visit Tymoshenko in the northern town of Kharkiv, where she is receiving hospital treatment under prison guard.
Before their arrival, Yanukovich, whose pro-Europe course has upset Russia, Ukraine's biggest trade partner, told a regional economic forum the Vilnius accords would mark "the beginning of a process of broader and deeper integration".
He made no specific reference to Tymoshenko or the efforts to reach a compromise on her case.
EU foreign ministers are due at a pre-summit meeting on November 18 to assess whether Kiev has met key democratic criteria, including ending what the bloc calls "selective justice", to allow for the signing to go ahead.
The EU mediators are focusing their attention on a compromise under which Tymoshenko, 52, can travel to Germany to receive medical treatment for spinal problems.
The Ukrainian parliament, dominated by pro-Yanukovich deputies and allies, is now haggling over the wording of a draft law that would allow her to travel abroad - the crux being whether she goes as a free person or as a convicted criminal.
Yanukovich, who only narrowly beat her in a run-off vote for president in February 2010, has balked at granting her a pardon.
Political analysts say he wants her politically side-lined when he makes his bid for a second term in early 2015.
Her supporters want a "full amnesty" so she can be cleared of her jail sentence and be free to return to politics one day.
Pro-Yanukovich deputies are pushing for a tougher draft which would mean she would have to return to Ukraine to complete her sentence after medical treatment.
The conditions attached by the Yanukovich camp to any release of Tymoshenko to Germany could have a direct bearing on any decision made at the November 18 EU meeting.
The EU is split between states such as Poland, which stress the need to prise Ukraine away from Russia's embrace, and those like Sweden and the Netherlands, which argue the bloc should not compromise on principles of civil rights and justice.
Source: Yahoo News