* U.S. Senator Kerry tours Hamas-ruled Gaza Strip
* Kerry says Hamas provoked Gaza war
* Hamas calls Kerry's criticism unfair
* Hamas give Kerry letter to Obama
(Adds Hamas letter to Obama, paragraphs 4-5 )
By Nidal al-Mughrabi
GAZA, Feb 19 (Reuters) - The highest-ranking U.S. delegation to visit the Gaza Strip in years toured bomb-damaged buildings on Thursday and blamed the enclave's Hamas rulers for provoking Israel's wrath with cross-border rocket attacks.
Senate Foreign Relations Committee Chairman John Kerry and two members of the House of Representatives, Brian Baird and Keith Ellison, shunned Hamas during tours one month after Israel ended its 22-day Gaza offensive.
It was the highest-level visit by U.S. legislators to the Gaza Strip since a Palestinian uprising against Israel erupted in 2000, U.S. officials in the region said. Kerry, who ran an unsuccessful campaign for president in 2004, earlier toured the Israeli border town of Sderot, a frequent target of rockets.
During his visit to a U.N. compound in Gaza, Kerry was given a letter from Hamas to deliver to President Barack Obama.
UNRWA spokesman Christopher Gunness said the letter had been left for Kerry at the gate of the compound and that he did not know the content. "We don't open other people's mail," Gunness said. Kerry's office had no immediate comment.
Though major fighting has stopped, tensions remain high. Israel bombed smuggling tunnels along Gaza's border with Egypt and militants fired a rocket that landed near Sderot.
During his visit to Gaza, Kerry, a member of Obama's Democratic party, toured the bombed-out American School and asked administrators whether Israel was letting in enough supplies for the Gaza Strip's 1.5 million residents.
Israel allows humanitarian aid into the impoverished enclave but has ruled out fully opening its border crossings to materials needed for reconstruction until Hamas frees an Israeli soldier captured in a 2006 cross-border raid.
"I know President Obama is committed to trying to resolve some very, very difficult issues," said Kerry, escorted by U.N. security personnel during his brief tour of the school.
Sharhabeel al-Zaeem, a member of the school's board, told Kerry that Israel was supplying only "the minimum" of what was needed and complained that ordinary Palestinians felt isolated because of the Israeli-led and Western-backed blockade of Gaza.
As chairman of the Senate committee, Kerry can influence U.S. foreign policy and aid.
Hamas won a 2006 Palestinian election and seized control of the Gaza Strip 18 months later after routing Fatah forces loyal to Western-backed Palestinian President Mahmoud Abbas.
The United States and the European Union boycott the Islamist group, which they consider a terrorist organisation, over its refusal to recognise Israel, renounce violence and abide by interim peace deals with the Jewish state.
"Your political leadership needs to make critical decisions and make it clear how it is willing to move to make peace, and those fundamental decisions have not been made," Kerry told Zaeem and others at the school.
"Secondly, your political leadership needs to understand that any nation that has rockets coming into it over many years, threatening its citizens, is going to respond," Kerry said.
Zaeem responded by comparing the plight of Palestinians in Hamas-ruled Gaza to a hostage crisis.
"A police officer won't be able to take a decision to destroy the whole building, killing all the hostages and the kidnappers?" Zaeem asked.
Kerry said: "You know, what is important is not to have a debate that goes backwards. It is important to go forwards. There is a clear path forward...Help us find peace."
Kerry did not elaborate on the path forward.
Hamas spokesman Fawzi Barhoum described Kerry's visit as a "step in the right direction to end the isolation of the Gaza Strip" but described his comments about Hamas as "unfair to the democratic choice of the Palestinian people."
The war in Gaza, which Israel launched with the declared aim of halting militants' rocket fire, killed more than 1,300 Palestinians, destroyed some 5,000 homes and ruined much of Gaza's infrastructure, local officials say.
Kerry said the U.S. policy of shunning Hamas was unchanged. (Additional reporting by Adam Entous in Jerusalem; writing by Adam Entous; editing by Tim Pearce) (For blogs and links on Israeli politics and other Israeli and Palestinian news, go to blogs.reuters.com/axismundi)