The icy rhetoric between top US officials and Israeli Prime Minister Benjamin Netanyahu escalated on Wednesday with Netanyahu accusing the US of allowing Iran to develop nuclear weapons and Secretary of State John Kerry questioning the prime minister's judgment on the issue.

The comments heightened the tension in the already strained relationship between the two allies ahead of Netanyahu's speech to Congress next Tuesday, being given at the behest of Republican lawmakers. More Democratic members of Congress announced they would skip the speech, which was orchestrated without the White House's knowledge.

Netanyahu wants his speech to strengthen opposition to a possible nuclear deal with Iran, a key foreign policy objective for President Obama. Iranian and US officials reported progress on a deal to regulate Tehran's nuclear activities, causing the Israeli PM to lash out at his usually staunch ally.

"It appears that they have given up on that commitment and are accepting that Iran will gradually, within a few years, develop the capabilities to produce material for many nuclear weapons…They might accept this, but I am not willing to accept this," he said in Israel, speaking in reference to the US as well as other world powers.

Netanyahu speech 'destructive'

John Kerry, speaking before a congressional hearing, dismissed Netanyahu's concerns, referring to a 2013 agreement with Iran.

"Israel is safer today with the added time we have given and the stoppage of the advances in the nuclear program than they were before we got that agreement, which - by the way - the prime minister opposed," Kerry said on Wednesday. "He was wrong."

On Tuesday, National Security Adviser Susan Rice called the plans for the prime minister's speech "destructive" to US-Israel relations. The comments by Kerry and Rice suggest the Obama administration will not mask its frustrations at Netanyahu's visit.

Many Democrats have said they will skip the speech, which Senator Tim Kaine called "highly inappropriate" in light of Israel's general elections on March 17. Other top officials, including Kerry and Vice President Joe Biden, scheduled trips out of the country to coincide with the event after it was announced.

President Obama won't meet with Netanyahu, citing the White House's policy against meeting with foreign leaders facing elections, although the purportedly sour relationship between the two leaders has been heavily discussed in recent years.

es/gsw (AP, Reuters)