US congresswoman Rashida Tlaib has rejected Israel's offer to allow her to visit her grandmother in the West Bank.

Ms Tlaib has criticised the "oppressive conditions" set for the visit as humiliating.

"I have decided that visiting my grandmother under these oppressive conditions stands against everything I believe in -- fighting against racism, oppression & injustice," she said in a tweet.

Earlier, Israel had said it would all allow Ms Tlaib, who is of Palestinian origin, to visit her elderly grandmother.

The decision taken by Interior Minister Aryeh Deri came a day after a controversial Israeli announcement that it would bar a planned weekend visit by Ms Tlaib and fellow Muslim congresswoman Ilhan Omar.

It took the action over their support of a boycott of Israel for its treatment of the Palestinians.

Ms Tlaib's grandmother (pictured with son) is in her 90s

 The decision to allow a "humanitarian visit" followed a pledge in a letter from the politician to "respect conditions imposed by Israel", the ministry said in a statement.

Tlaib had "promised not to promote the cause of the boycott of Israel during her stay", in the letter sent overnight, it said.

Israeli media published the letter, which said: "I would like to request admittance to Israel in order to visit my relatives, and specifically my grandmother, who is in her 90s.

"This could be my last opportunity to see her. I will respect any restrictions and will not promote boycotts against Israel during my visit." 

The initial decision to bar the congresswomen, although encouraged by US President Donald Trump, drew sharp criticism in the United States from several allies of Israel, including top Democratic politicians, presidential hopefuls and influential pro-Israel lobby AIPAC.