PARIS — President Barack Obama is putting increasing pressure on European officials to resolve the euro crisis, talking with the leaders of Germany, France and Italy to help lay the groundwork for action before a Group of 20 summit meeting to be held in June in Mexico.


Mr. Obama discussed the recent developments in Europe in video conference calls with the European leaders on Wednesday. Mr. Obama was following up on discussions he held at the recent Group of 8 meeting at Camp David with the German chancellor, Angela Merkel, the French president, François Hollande and Mario Monti, the Italian prime minister.


“Leaders agreed to continue to consult closely as they prepare to meet at the G-20 summit in Mexico
next month,” the White House said in a statement. The meeting will be held June 18-19, beginning just a day after a Greek election that is being seen as a de facto referendum on that country’s euro membership.


The White House has also dispatched Lael Brainard, a Treasury under secretary, to Europe this week for talks with officials in Greece, Germany, Spain and France.


“The U.S. has doubts about its own pace of growth, it sees China slowing, and Europe is confronting a recession,” Hervé Goulletquer, head of fixed-income market research at Crédit Agricole, said. “If there is a deeper crisis in Europe, it will be an impediment for growth in the U.S., it will be a big issue for the country and for Obama as a candidate.”


Washington, is “pushing for more action in Europe,” Mr. Goulletquer said, “but I think everyone in Europe knows something has to be done.”


In Ireland, voters were going to the polls Thursday for a referendum on the European Union fiscal treaty
for fostering budgetary discipline and growth. While polls have shown a small majority favoring the treaty, the Irish are already resentful of painful austerity measures, and success is not certain. A failure to back the agreement could mean that Ireland was unable to draw on European Union financing after 2013 if it needs another bailout and could further encourage anti-euro sentiment in Europe.


Final results will be known only on Friday.


The main concern on investors’ radar remains Spain, which is searching for a way to recapitalize its struggling financial sector. The government had to nationalize Bankia, a foundering mortgage lender, in May, and the bank said Friday that it would need 19 billion euros, or almost $24 billion, in new rescue funds. The austerity-strapped government with little in its arsenal to help other troubled lenders, and borrowing in the market has become prohibitively expensive, at around 6.5 percent for 10-year debt.


The situation has led to increasing capital flight, with the E.C.B. reporting that deposits in Spanish banks in April by 31.5 billion euros. Amadeu Altafaj, a spokesman for the European Commission, said the government in Madrid needed to move quickly to reassure investors.


“What you cannot do is maintain this uncertainty, which is what is dragging down market confidence,” The Associated Press quoted him as saying on Spanish National Radio.


“Spain is ‘too big to fail’ as far as the euro is concerned,” Charles Diebel, head of market strategy at Lloyds Banking in London, wrote in a research note. “And the funding issues and lack of viable bank resolution are causing an investor flight as seen before, but the numbers and magnitude are on a different level from anything seen thus far. We could be fast approaching a situation where the sanguine outlook maintained by some politicians in core countries cannot be sustained.”


Fitch Ratings on Thursday cut its ratings on eight Spanish regions, including Madrid and Catalonia, to one notch above junk, and said the outlook for all the regions was negative. Fitch said the action reflected “the negative economic and market environment in Spain, which has resulted in depressed fiscal revenues, and the structural fiscal deficits of the regional administrations, which will require considerable additional efforts to be reduced, and also the difficulties in accessing long-term funding.”


The Spanish deputy prime minister, Soraya Saenz de Santamaria, was scheduled to meet later Thursday with Treasury Secretary Timothy F. Geithner and the International Monetary Fund managing director, Christine Lagarde, in Washington. An I.M.F. spokesman in Washington said Spain had not requested any financial support from the fund.