LONDON (Reuters) - Foreign secretary Boris Johnson said on Monday that a key proviso of a 100-year old British declaration which laid the foundations for Israel had not been fully met, striking a sympathetic tone towards the Palestinians.

Britain's Foreign Secretary Boris Johnson gives a speech at the British Embassy during his European tour on Brexit, in Paris, France, October 27, 2017. REUTERS/Geoffroy Van Der Hasselt/Pool

Israeli Prime Minister Benjamin Netanyahu is due to travel to Britain on Thursday to meet his British counterpart Theresa May and Johnson for the anniversary of the Balfour declaration which said Britain viewed with favor “the establishment in Palestine of a national home for the Jewish people”.

Palestinians have long condemned the declaration - named after Arthur Balfour, then the British foreign secretary - as a promise by Britain to hand over land that it did not own.

In an article written for the Daily Telegraph newspaper ahead of Netanyahu’s visit, Johnson described himself as a “friend of Israel”, but also said he was “deeply moved by the suffering of those affected and dislodged by its birth.”

“The vital caveat in the Balfour Declaration - intended to safeguard other communities - has not been fully realized,” he said referring to the clause in the document which said nothing should prejudice the civil and religious rights of existing non-Jewish communities.

May met Netanyahu earlier this year to talk about boosting trade after Brexit, but also raised the diplomatic sore point of Israeli settlements in occupied lands on which the Palestinians hope to create an independent state.

Johnson also made reference to the settlement issue in his article, saying that a two state solution must include a viable and contiguous Palestinian state alongside a “secure Israel”, and proposed seeking a peace agreement based on 1967 borders with mutual territorial swaps.

A similar call in 2011 by then-U.S. president Barack Obama drew a blunt rebuke from Netanyahu, who said Israel would never pull back to its 1967 borders - something which would mean big concessions of occupied land. Netanyahu contends this would leave Israel with indefensible borders.

Palestinian President Mahmoud Abbas called on Britain last year to apologize for the Balfour Declaration, saying that his people had suffered greatly as a result of it.

Earlier this year Britain said it there would be no apology for the declaration, and said it continued to work for an Israeli-Palestinian peace deal.

Britain does not classify Palestine as a state, but says it could do so at any time if it believed it would help peace efforts between the Palestinians and Israel.