Western leaders are coming out more strongly in support of Ukrainian opposition demands, as mass protests persist in Kiev after the government abandoned a planned accord with the European Union. In a declaration Tuesday, foreign ministers of the 28 NATO member states, including US Secretary of State John Kerry, took a moderate line urging the government and the opposition "to engage in dialogue and launch a reform process". But on Wednesday, Kerry weighed in personally during a visit to neighbouring Moldova, saying Ukrainians had the right to "choose their own future" without external pressures, in an apparent reference to Russia which Kiev said forced its hand in backing out of the deal. German Foreign Minister Guido Westerwelle flew into Kiev on Wednesday for a meeting of the Organization for Security and Cooperation in Europe (OSCE) and headed straight to Kiev's Independence Square where he spoke to protesters in person. He travelled to the square -- the centre of Ukraine's 2004 Orange Revolution -- on foot, accompanied by opposition leader and boxing champion Vitali Klitschko, who trains in Germany. "The gates of the European Union are still open. Ukraine has to be on board in Europe and the offers from Europe are still valid," Westerwelle told reporters after the meetings. President Viktor Yanukovych dropped the association accord just before a high-profile summit with the EU last week after Russia made clear the former Soviet republic would pay a high price for deserting Moscow's fold. The decision sparked street demos in Kiev and dismay in Brussels, which had seen the association deal as a major achievement in bringing Eastern Europe closer to the EU. The OSCEs Secretary General Lamberto Zannier and the organisation's Chairperson in Office, Ukrainian Foreign Minister Leonid Kozhara, discussed the crisis on the eve of its ministerial council meeting. Zannier said he welcomed assurances from Kozhara that "Ukraine would respect citizens' right to peacefully protest and that recent incidents of excessive force were being investigated". 'All sides should enter dialogue peacefully' "Respect of fundamental rights, such as freedom of assembly, the right to free expression and giving journalists the liberty to do their work is essential to ensuring cohesive and secure societies," he said in a statement. "All sides should enter dialogue peacefully and without resort to violence or other actions which prevent constructive engagement." NATO has condemned the "use of excessive force against peaceful demonstrators in Ukraine", in response to a police crackdown on pro-Europe protesters at the weekend. Russian Foreign Minister Sergei Lavrov denounced the NATO declaration as unwarranted interference in Ukraine's domestic affairs, but analysts said it was merely a restatement of the West's position. "The tone of the declaration is rather moderate," said one European diplomat. "This is about trying to avoid upsetting Russia just as we are working well together on the Iranian nuclear issue and destroying Syria's chemical weapons arsenal," the diplomat said, asking not to be named. For Lavrov, however, the declaration was part of outside efforts to muddy the waters in Ukraine. "I do not understand why NATO adopts such statements," Lavrov said after Wednesday's meeting of the NATO-Russia Council, part of the two-day foreign ministers' gathering. "It helps to create a distorted picture and sends a wrong signal which may cause wrong understanding," he said, adding that whether Ukraine seeks closer ties with the European Union is "a domestic issue". Kerry made clear that Washington remains unhappy about events in Ukraine by cancelling a trip to Kiev to attend Thursday's OSCE meeting. Instead, he chose to continue on to Moldova, the tiny former Soviet state which alongside Georgia opted to sign partnership deals with the EU last week despite Moscow's warnings.