Already set to be the “largest military aid package” the US has ever offered to a single country in history, the Obama Administration has written a lengthy letter to US Senators today, informing them of intentions to “substantially sweeten” the already record offer in an attempt to try to get the Israelis to sign on the dotted line.

A $30 billion, 10-year aid package is due to expire, and the new package has been rumored to be in the realm of $37.5 billion, with talk it might go to as high as $40 billion as the Netanyahu government continues to resist signing it.

The latest push comes just a week after Republican presidential front-runner Donald Trump’s top Israel adviser urged Israel to refuse any deal with Obama, promising much more if Trump is elected. Several Israeli officials have warned such a move could significantly shift US-Israel relations, making them a partisan issue.

Few details are clear about the new letter’s offer, though unchanged is the administration’s effort to ensure that Israel spends a larger percentage of the military aid on US-made weapons. Under the present deal, Israel is allowed to spend about 25% of the aid elsewhere, both on fuel and on funding their own programs.

While all indications are that funding for Israeli missile defense schemes will be baked into this new pact, the overall percentage allowed to be spent abroad is expected to drop significantly, which makes this as much a US subsidy for its well-connected arms makers as it is an aid package for Israel.