Prime Minister Helen Clark's spokesman said Sunday that words of regret from Israel's president over a scandal involving suspected Israeli spies were encouraging, but that New Zealand has yet to receive a formal apology. Relations between the two nations have been frosty since two suspected Israeli agents were convicted and imprisoned in New Zealand for trying to fraudulently obtain a passport in 2004. New Zealand has demanded a public explanation and apology for what Clark described as "utterly unacceptable" behavior by the two, Uriel Zoshe Kelman and Eli Cara. They were deported last year after serving half of their six-month prison sentences. Police are still searching for several other people they believe were involved. Clark has slapped diplomatic sanctions on Israel, including delaying approval of the appointment of a new Israeli ambassador. She also postponed foreign ministry consultations and declined to issue an invitation for Israel's President Moshe Katsav to visit New Zealand. Katsav said on Australian television that he regretted the deterioration of his country's relationship with New Zealand. "I am very sorry about the last development in our relations with New Zealand." Katsav said on Channel Nine Television's Sunday program. "For us New Zealand is a good friend of Israel and I really regret about what happened." "But again, I really hope that this problem is closed and I want really to close this chapter in our relation with New Zealand. I can express my (sorrow) and my regret," he said. Clark's spokesman said the comments were encouraging, and her government looked forward to making progress on the matter through diplomatic channels.