Hamas will not do Iran's bidding in any war with Israel, according to senior figures within the militant Islamic group.

"If there is a war between two powers, Hamas will not be part of such a war," Salah Bardawil, a member of the organisation's political bureau in Gaza City, told the Guardian.

He denied the group would launch rockets into Israel at Tehran's request in response to a strike on its nuclear sites. "Hamas is not part of military alliances in the region," said Bardawil. "Our strategy is to defend our rights"

The stance underscores Hamas's rift with its key financial sponsor and its realignment with the Muslim Brotherhood and popular protest movements in the Arab world.

Bardawil's words were echoed by a second senior Hamas figure, who declined to be named. Hamas, he said, "would not get involved" in any war between Iran and Israel.

Speculation in Israel about the repercussions of a military strike on Iran has encompassed the likelihood of the Jewish state coming under sustained rocket fire from Hamas in Gaza and Hezbollah in Lebanon. Both organisations are routinely described by Israeli officials as "proxies" for the Iranian regime.

However, Hamas has never given "complete loyalty" to Tehran, said Bardawil, pointing out that Iran's population is overwhelmingly Shia, whereas Gaza is Sunni. "The relationship was based on common interests."

Tehran has withdrawn its patronage of Hamas over the Palestinian group's refusal to support the Syrian regime against a year-long uprising. According to a Gazan academic who specialises in Islamic movements, this has included the termination of financial support worth $23m (£14.5m) a month.

"Iran is very unhappy about Hamas and Syria, so it is punishing Hamas," said Adnan Abu Amer of Ummah university. "They have stopped funding. Hamas has other sources – the Gulf states, Islamic movements, charities – but all of these together are not comparable to $23m a month."

Bardawil denied this sum, saying "the money that comes from Iran is very limited. In the early days of the [Israeli] blockade [of Gaza], the money was very good, but it was reduced two years ago." The cut in funding "is not because of the Syrian revolution," he added.

Abu Amer, who had links to both Hamas and the Syrian government during three years in Damascus studying for a PhD, likens the rupture between the two sides to a divorce. "Syria has become the past for Hamas. It's not a complete divorce, but the love will not return. Both sides understand this."

Khaled Meshaal, the exiled leader of Hamas, was the second most important person in the country after President Bashar al-Assad, said Abu Amer. "The hotline between them was unique." Hamas leaders in Syria were treated like members of state, he said. "The regime even allowed Hamas people to hold weapons. It was like a military base for Hamas."

But the uprising against the regime put Hamas in a critical position. "For 10 months, Hamas kept silent in public about the Syrian revolution, neither for it nor against it. But inside Hamas, there was another revolution – arguments within the leadership over the killing of Syrian people," said Abu Amer.

"The exiled leadership was frozen, because they had no other place to go. But others, in Gaza and elsewhere, wanted to speak out against the killings, especially the clerics. This was a burden on the leadership."

In addition, the Muslim Brotherhood in the region was openly critical of the Syrian regime and urged Hamas to break with Assad. In particular, the influential Islamic cleric Yusuf al-Qaradawi put personal pressure on Meshaal, said Abu Amer.

Bardawil confirmed the dilemma for the exiled Hamas leadership. "When the bloodshed increased, it was hard ethically not to express sadness. Hamas always stands with the people, not the regimes, but that does not mean holding a weapon to take part in military action against the regime."

The Muslim Brotherhood exerted an influence, he said. "Hamas has been part of the Muslim Brotherhood from the beginning. The leadership has a very tight relationship with the Brotherhood leadership." The connection between the two organisations was based on ideology, he said, whereas the relationship between Hamas and Syria was strategic.

Hamas has been careful not to completely cut its ties with Syria despite the relocation of the leadership to other countries. "There are still a few Hamas members in Damascus," said Abu Amer. "And those who left have not made public statements against the regime. Both sides need back-up."

According to Bardawil, the Hamas office in Damascus "is still open and functioning, but is empty. We still haven't found another country to move our office to." The external leadership is now scattered across Jordan, Qatar and Egypt, with one politburo member, Imad al-Alami, returning to Gaza after a 20-year absence.

Some observers say the fragmentation of the external leadership of Hamas has inevitably strengthened the hand of the internal Gaza-based leadership headed by the de facto Gaza prime minister Ismail Haniyeh and Mahmoud Zahar. Frictions between the two sets of leaders have grown in recent months, particularly over the issue of political reconciliation between Hamas and its rival, Fatah. Meshaal has pushed hard for a rapprochement; Haniyeh and Zahar are resistant.

In an unexpected and forceful show of solidarity in a speech in Cairo last month, Haniyeh saluted "the heroic people of Syria who are striving for freedom, democracy and reform". The move explicitly underlined Hamas's rift with the regime.

According to Abu Amer, the external leadership was uncomfortable with Haniyeh's public stance. But more statements could be expected in the future, he said. "It will gradually become more public. But the clearer, stronger statements will come from Hamas in Gaza."

Hamas, he said, wants to be part of the Arab Spring. "The revolutions in the Arab world and the rise of Islamic movements affected Hamas. Hamas read it very well." The organisation was realigning itself with ascendant Islamist movements which are more oriented towards elections and reaching out to the West than armed resistance. "Hamas cannot be asked to erase the history of 25 years in one day. But it's coming."

Indicative of that was unofficial back-channel contacts between western officials and representatives of Hamas. Bardawil said that he and Zahar met a delegation of Europeans and Americans in Cairo last May, and there had been subsequent meetings with different Hamas representatives. He declined to give details but said: "We are asking to have those channels and connections to western countries. We want to tell our story."

• This article was amended on 7 March 2012. The original said: "When the bloodshed increased, it was hard ethically not to express sadness. Hamas always stands with the people, not the regimes, but does that not mean holding a weapon to take part in military action against the regime." This has been corrected.