OSLO (Reuters) -Norway's prime minister said on Friday he had contacted U.S. Senator Lindsey Graham to try to defuse a controversy over a decision by the Norwegian sovereign fund to sell all its shares in construction equipment group Caterpillar on ethics grounds.

Norway's $2 trillion sovereign wealth fund, the world's largest, said on Monday it had divested from Caterpillar over ethical concerns due to the company's supply to Israel of bulldozers used in the occupation of Gaza and the West Bank.

Caterpillar did not comment on the wealth fund's move. 

Graham, an ally of President Donald Trump, said on Thursday that Norway should reconsider its decision or risk facing new U.S. trade tariffs on its exports or have visa travel restrictions imposed on the fund's managers.

"Your decision to punish Caterpillar, an American company, because Israel uses their product is beyond offensive," Graham wrote on X. "I would urge you to reconsider your shortsighted decision," he later added.

About 52% of the fund's assets, more than $1 trillion, were held in the U.S. as of June 30, spread across equities, Treasuries and real estate.

ARM'S LENGTH

Management of the assets is designed to be at arms-length from the government, and the decisions on which companies to divest from are made by the board of the central bank, which operates the fund.

The Caterpillar divestment was decided at the recommendation of the fund's Council on Ethics, a public body set up by the Ministry of Finance to check that firms in the portfolio of the fund meet ethical guidelines set by Norway's parliament.

"Yesterday afternoon (Thursday), the prime minister informed Senator Lindsey Graham about the organisation of the pension fund via a text message," State Secretary Kristoffer Thoner of Prime Minister Jonas Gahr Stoere's office said in a statement to Reuters.

"The decision to exclude companies is an independent decision made by the board of Norges Bank, in accordance with the established framework," he added. 

"This is not a political decision."

Graham confirmed he had received the message, Thoner said.

Graham's office did not immediately respond to a request for comment.

The Norwegian fund, built from vast oil and gas revenues, is invested in some 8,400 companies, owning 1.5% of all listed stocks globally.

Some commentators in the Nordic country have asked whether, given the uncertainties about economic policies under Trump, there could be a risk to the fund's U.S. assets, such as asset seizure or a forced debt swap.

Asked in April this year what he made of such scenarios, the fund's CEO Nicolai Tangen said he did not see a credible risk of asset seizure.