Speaking at a reception hosted by the US Chamber of Commerce and US-Asean Business Council, PM Lee acknowledged that the politics are difficult in an election year in the US but said that ratification of the 12-nation pact would be a “clear statement” of the US posture in the region.

“Every one of the TPP signatories has had to make sacrifices in order to accept the TPP agreement. There is no appetite to re-open negotiations again…with no prospect of doing better and every chance of it falling apart,” he said.

“Asian countries want America to be engaged. But we need to know that this engagement will be sustained. We need to know that agreements will be upheld. And that Asia can depend on America. Your ratification of the TPP will therefore be a clear statement of your commitment and confidence to our region.”

The landmark agreement was agreed to last year after a prolonged negotiation process. The deal now awaits ratification by the various domestic legislatures of the countries party to the deal. Apart from the US and Singapore, the pact includes countries such as Japan, Vietnam and Malaysia.

Ratification by the US Congress has long been considered among the most uncertain, given election year politics. Both Republican nominee Donald Trump and Democratic nominee Hillary Clinton have said they oppose the deal.

President Barack Obama, however, told The Straits Times in an interview that he “remains committed” to the deal.

In his address at the reception, PM Lee also reiterated the many strategic and economic advantages the deal holds for the US.

Noting that the TPP will represent 40 per cent of the global GDP and a market of 800 million people, he said it would be an “economic game-changer” for America.

“Improved market access will mean cheaper products for consumers and more exports for manufacturers. Incorporated in the TPP are provisions on human rights, intellectual property protections and safeguards for labour and the environment. Strong standards will support innovation and benefit many US technology giants.”

Strategically, he said the deal would also add substance to the US rebalance to Asia, which he stressed cannot just be about the military and the 7th Fleet.

“There are no winners, only losers with protectionism. Economic development across the world will be stymied.  With less interdependence, the bulwark against conflict and war is weakened,” he said.

“As Americans say, be at the table, or be on the menu,” he added.

During the dialogue session that followed, PM Lee was asked how the working class Americans feeling the strain of globalisation might be convinced of the value of free trade deals.

Lee said that while trade does produce net benefits, those are not necessarily accrued evenly to everyone. The job of the government is to ensure that the net benefits can be shared.

“There will be those who benefit less and those who don’t benefit and I think that your political system should look after them,”he said.

Earlier in the day, the Singapore prime minister met US Treasure Secretary Jacob Lew, Defence Secretary Ash Carter and Commerce Secretary Penny Pritzker. He also laid a wreath at Arlington National Cemetery and was received at the Pentagon with an enhanced honour cordon, featuring a US military band playing the Singapore national anthem.

PM Lee meets President Obama on Tuesday in the White House and will also be hosted to a state dinner, one of the highest diplomatic honours bestowed by the US government.