BRUSSELS, Feb. 4 -- It has been a busy Wednesday for new Greek Prime Minister Alexis Tsipras and his Finance Minister Yanis Varoufakis as they were lobbying across Europe for a solution to its debt.

European Council President Donald Tusk stressed in a statement after meeting Alexis Tsipras in Brussels the necessity of finding a solution acceptable to all member states involved in the negotiations concerning European financial assistance to Greece.

The negotiations will "be difficult" and "require cooperation and dialogue as well as determined efforts by Greece", said Tusk.

He said they two had agreed on the importance of unity within the European Union (EU) with regard to other key challenges facing Europe.

Tsipras, who also visited the European Parliament (EP) in Brussels, was complimented by EP President Martin Schulz as "battling for European cooperation, not only seeking a solution for Greece". Schulz extended his full support for him.

Schulz stressed the need for a framework for "constructive dialogue and solutions", while Tsipras said he was optimistic that they were moving in the right direction for a sustainable solution.

On the same day, Tsipras also rushed to Paris, where he had a meeting with French President Francois Hollande.

Hollande called for a transparent and serene dialogue over Greek debt crisis, and also for the respect of EU financial rules.

"A dialogue should take place in transparency and serenity. It should be strengthened to lead to an agreement," Hollande said.

The French head of state also stressed that Europe should work more to further cement solidarity via pro-growth measures which could help the bloc to boost economic activities and tackle unemployment headache.

"Austerity as the only perspective and reality wasn't tolerable anymore," Hollande said at a joint press meeting with Tsipras.

As the leftist Greek rulers are seeking support for a new debt accord, Hollande stressed the eurozone's rules applied to everyone.

"There is respect for European rules, which are imposed on everyone, to France as well, and it's not always simple. And then there is respect for commitments that have been made," he told reporters at the Elysee Palace.

Tsipras said: "We are not a threat to Europe. Political change can present an opportunity for it."

"We need a new agreement which will pave the way for a return to growth and boost employment. And France has to play a leading role of guarantor for a policy change in Europe," he said.

Meanwhile, Greek Finance Minister Yanis Varoufakis said in Frankfurt he was encouraged after talks with European Central Bank (ECB) president Mario Draghi.

Varoufakis told reporters that the meeting was "fruitful" and he described the talks as an "excellent line of communication, which gives me a great deal of encouragement for the future."

Varoufakis said he presented to Draghi the Greek government's plan and expressed the determination that "it can't possibly be business as usual for Greece."

According to Varoufakis, Draghi was very helpful and outlined how the ECB supports eurozone member states including Greece. The ECB declined to comment on the meeting.

Greek debt exceeds 320 billion euros (365 billion U.S. dollars), 175 percent of its gross domestic product. The Greek government has been negotiating with international creditors on its bailout deal. It has to get access to additional bailout funds by the end of this month to avoid a default on maturing loans.

Varoufakis has proposed that Greece raise 10 billion euros (11.45 billion U.S. dollars) by issuing short-term treasury bills, which needs approval from the ECB.

Back in Greece, 812.5 million euros (about 926 million U.S. dollars) were raised in the latest treasury bill sale on Wednesday, the first under the new Radical Left SYRIZA-led coalition government at increased cost, according to the country's Public Debt Management Agency (PDMA).

Analysts in Athens attributed the increased cost to the prevailing uncertainty over the new government's economic policy and the result of renegotiations with Greece's creditors on the management of the debt crisis.