Prime Minister Lee Hsien Loong met United States Secretary of Commerce Penny Pritzker and US Treasury Secretary Jack Lew on Monday, the first day of his working visit to the United States this week.

Both meetings touched on the bilateral ties between Singapore and the US as well as the progress of the Trans-Pacific Partnership (TPP), the ambitious free trade pact currently being negotiated between 12 nations including Singapore and the US.

In their meeting, Mr Lee and Ms Pritzker "noted the progress made in the TPP negotiations and the consequential role the TPP plays in the US' engagement of the Asia-Pacific region", according to a statement by the Prime Minister's Office (PMO).

Mr Lee and Ms Pritzker also discussed ways to enhance economic ties, not just bilaterally but also between the US and Asia Pacific.

After the meeting, Ms Pritzker tweeted a picture of herself and Mr Lee, saying the two had a "great meeting".

"We value our mutually beneficial economic relationship," she added.

With Mr Lew, Mr Lee exchanged views on regional and international developments, including the global economic and financial outlook and the progress of the TPP talks.

Mr Lee told Mr Lew that he welcomed the US' commitment to further intensify its engagement of the Asia-Pacific region, according to a PMO statement.

Both sides "affirmed the excellent bilateral relations between Singapore and the US, and discussed ways to further strengthen bilateral cooperation."

Mr Lee's visit to the US will continue until Thursday.