Feb 22 (Reuters) - Pfizer Inc expects to deliver more than 13 million doses of its COVID-19 vaccine per week to the United States by the middle of March, more than doubling its shipments from early February, a top Pfizer executive said in prepared testimony ahead of a Tuesday congressional hearing.

Pfizer is on track to deliver 120 million doses of its two-dose regimen by the end of March, said John Young, Pfizer's chief business officer.

Pfizer is also prepared to provide a total of 300 million shots to the United States by the end of July and has raised global production expectations for 2021 to at least 2 billion doses, he said.

In his own prepared remarks, Moderna Inc President Stephen Hoge said the drugmaker plans to deliver 100 million doses of its two-dose shot by the end of March, and 300 million by the end of July.

Johnson & Johnson believes it will be able to ship at least 20 million doses of its single-dose shot to the United States by the end of March after receiving U.S. regulatory authorization and 100 million doses by mid-year 2021, said Vice President of Medical Affairs Richard Nettles.

The comments were prepared ahead of a U.S. congressional hearing on vaccine availability to be held by the House Committee on Energy and Commerce on Tuesday as the United States crossed the staggering milestone of 500,000 COVID-19 deaths.

The remarks put the United States on track to receive 240 million doses by the end of March, enough to inoculate 130 million Americans, and 700 million doses by mid-year.

AstraZeneca Plc, which is running a U.S. trial for its coronavirus vaccine, believes it can quickly adapt its shot to new variants of the virus in its laboratory, said Ruud Dobber, company president, North America.

A highly contagious COVID-19 variant has become prevalent in South Africa and has turned up in several U.S. states. (Reporting by Carl O'Donnell in New York Editing by Rosalba O'Brien, Matthew Lewis and Ana Nicolaci da Costa)