The agreements help solidify the relationship between the countries; Venezuela has played an important role in helping Mr. Kirchner revive Argentina's still-recovering economy.

But they are also causing potential political problems. In recent days, Jewish leaders here -- part of Latin America's largest Jewish community -- have been expressing growing concern about Mr. Chavez's close ties to Iran.

On Monday, Mr. Chavez and Mr. Kirchner agreed that Venezuela would purchase $1 billion of Argentine bonds to help refinance Argentina's debt, according to an Argentine government Web site. A purchase would bring to nearly $5 billion the total debt that Venezuela has helped Argentina refinance in the past four years.

The two countries also agreed to build a plant in Argentina that will turn liquid natural gas from Venezuela into usable gas. The plant will allow Venezuela to send liquid gas to Argentina by ship, a shift in strategy for Mr. Chavez as discussions for a natural gas pipeline from Venezuela via Brazil have bogged down.

The gas conversion plant would be a joint project between Venezuela's state oil company, Petroleos de Venezuela, and the Argentine state oil company, Enarsa.

Mr. Chavez has worked scrupulously to forge closer ties with Argentina, which is still recovering from a near economic collapse in 2002. The failure of international lending agencies to bail Argentina out led Mr. Kirchner, who was elected in 2003, to seek closer ties elsewhere. Mr. Chavez, flush with oil profits, stepped in and helped refinance some of Argentina's debt at more favorable terms.

Mr. Chavez now has the ability to extend his influence in Argentina on the energy front. Argentina is suffering one of its worst energy crises in decades because of a lack of investment in drilling for new oil and natural gas deposits and an unusually cold winter.

Before Mr. Chavez's visit on Monday, Jewish leaders here and abroad had expressed worries that his largess would give him a freer hand to influence Argentine politics. Mr. Chavez has developed a close relationship with the Iranian president, Mahmoud Ahmadinejad, who has called for the destruction of Israel and whose country is suspected of being behind the 1994 bombing of a Jewish community center here that killed 85 people and wounded more than 200.

''The question is, will the economic agreements also generate some type of political commitment?'' said Sergio D. Widder, the Latin American representative of the Simon Wiesenthal Center, a Jewish human rights organization.

The issue could prove to be a thorny one for Cristina Fernandez de Kirchner, the president's wife and the leading candidate to succeed him in October elections.

Mrs. Kirchner is walking a delicate line between supporting Mr. Chavez and offering support to the Jewish community, which she has done consistently since her days as an opposition senator. Both Kirchners have supported recent efforts to solve the bombing case, even as investigators have increasingly focused on Iran's possible involvement.

After years of failed investigations, Mr. Kirchner appointed a special prosecutor, Alberto Nisman, who doggedly pursued the case. Last October, he issued a report on the bombing, concluding that the plot was hatched in Tehran. Mr. Nisman cited seven top-level former Iranian government officials, including a former president, and a Hezbollah operative. An Argentine judge approved the report and submitted it to Interpol, which issued arrest warrants for the eight.

Mr. Kirchner reportedly refused to attend the inauguration of President Rafael Correa of Ecuador in January because the Iranian president, Mr. Ahmadinejad, was present. The Kirchners have even met with Jews in Venezuela who unsuccessfully called on the Argentine leader to try to broker a meeting with Mr. Chavez.

In addition to being concerned that Mr. Chavez could try to leverage his economic relationship with Argentina to influence politics here and the investigation into the 1994 bombing, Jewish leaders are also worried that Mr. Chavez's anti-American statements could affect attitudes in Argentina.

''Jews are worried that Chavez's anti-Americanism could turn into anti-Semitism,'' said Meir Javedanfar, a Tel Aviv-based political analyst.

Mrs. Kirchner has given no indication that Argentina's support for Mr. Chavez would change if she is elected president on Oct. 28, as polls suggest she will be.

Two weeks ago on a campaign trip to Spain, she compared Mr. Chavez to President Vladimir V. Putin of Russia. ''The Latin American energy equation won't be solved without the presence of Venezuela and Bolivia,'' she said. ''Latin America needs Chavez like Europe needs Putin.''